1
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Abstract
Sixteen new thymol derivatives have been isolated from Eupatorium fortunei and their structures determined based on spectroscopic data. They were classified into three groups (i-iii) depending on the oxidation levels: (i) one oxygen function at the 9-position, (ii) two oxygen functions at the 8- and 9-positions, and (iii) three oxygen functions at the 8-, 9-, and 10-positions. The hydroxyl groups are acylated with tigloyl, angeloyl, acetyl, isobutyryl, 3-methyl-2-butenoyl, or 2-methylbutyryl moieties. The compounds having chiral centers showed no specific rotation and exist as racemic mixtures.
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Affiliation(s)
- M Tori
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan.
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2
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Abraham BD, Sono M, Boutaud O, Shriner A, Dawson JH, Brash AR, Gaffney BJ. Characterization of the coral allene oxide synthase active site with UV-visible absorption, magnetic circular dichroism, and electron paramagnetic resonance spectroscopy: evidence for tyrosinate ligation to the ferric enzyme heme iron. Biochemistry 2001; 40:2251-9. [PMID: 11329294 DOI: 10.1021/bi002121h] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Coral allene oxide synthase (AOS), a hemoprotein with weak sequence homology to catalase, is the N-terminal domain of a naturally occurring fusion protein with an 8R-lipoxygenase. AOS converts 8R-hydroperoxyeicosatetraenoic acid to the corresponding allene oxide. The UV--visible absorption and magnetic circular dichroism spectra of ferric AOS and of its cyanide and azide complexes, and the electron paramagnetic resonance spectra of native AOS (high-spin, g = 6.56, 5.22, 2.00) and of its cyanide adduct (low-spin, g = 2.86, 2.24, 1.60) closely resemble the corresponding spectra of bovine liver catalase (BLC). These results provide strong evidence for tyrosinate ligation to the heme iron of AOS as has been established for catalases. On the other hand, the positive circular dichroism bands in the Soret region for all three derivatives of ferric AOS are almost the mirror image of those in catalase. In addition, the cyanide affinity of native AOS (K(d) = 10 mM at pH 7) is about 3 orders of magnitude lower than that of BLC. Thus, while these results conclusively support a common tyrosinate-ligated heme in AOS as in catalase, significant differences exist in the interaction between their respective heme prosthetic groups and protein environments, and in the access of small molecules to the heme iron.
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Affiliation(s)
- B D Abraham
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
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3
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Abstract
Esters of trans-4-hydroxycinnamic acid, cis-4-hydroxycinnamic acid and trans-3,4-dihydroxycinnamic acid with long-chain alcohols (n=15-20), were isolated from the stems of Calystegia soldanella.
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Affiliation(s)
- M Tori
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro cho, Tokushima 770-8514, Japan.
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4
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Tori M, Shimoji T, Shimura SE, Takaoka S, Nakashima K, Sono M, Ayer WA. Four alkaloids, lucidine B, oxolucidine A, lucidine A, and lucidulinone from Lycopodium lucidulum. Phytochemistry 2000; 53:503-509. [PMID: 10731030 DOI: 10.1016/s0031-9422(99)00592-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The structures of four alkaloids extracted from Lycopodium lucidulum (Lycopodiaceae) were established by X-ray and 2D NMR spectroscopic analyses. The dihydro-derivative of oxolucidine A, which was obtained by NaBH4 reduction of oxolucidine A, was treated with p-bromobenzoyl chloride to afford crystals, whose X-ray crystallographic analysis established the stereostructure, including the absolute configuration. The 2D NMR spectra of tetrahydrodeoxylucidine B were fully analyzed to establish the full structure of lucidine B, and the hitherto unknown stereochemistry at the C-14 position was established as beta-H. The structure of a new alkaloid, lucidulinone, was determined by spectroscopic analysis to be luciduline lactam.
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Affiliation(s)
- M Tori
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Japan.
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5
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Sono M, Ledbetter AP, McMillan K, Roman LJ, Shea TM, Masters BS, Dawson JH. Essential thiol requirement to restore pterin- or substrate-binding capability and to regenerate native enzyme-type high-spin heme spectra in the Escherichia coli-expressed tetrahydrobiopterin-free oxygenase domain of neuronal nitric oxide synthase. Biochemistry 1999; 38:15853-62. [PMID: 10625450 DOI: 10.1021/bi991580j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitric oxide (NO) synthases (NOS) are thiolate-ligated heme-, tetrahydrobiopterin (BH(4))-, and flavin-containing monooxygenases which catalyze the NADPH-dependent conversion of L-arginine (L-Arg) to NO AND citrulline. NOS consists of two domains: an N-terminal oxygenase (heme- and BH(4)-bound) domain and a C-terminal reductase (FMN- and FAD-bound) domain. In this study, we have spectroscopically examined the binding of L-Agr and BH(4) to the dimeric, BH(4)-free ferric neuronal NOS (NNOS) oxygenase domain expressed in Escherichia coli separately from the reductase domain. Addition of L-Arg or its analogue inhibitors (N(G)()-methyl-L-Arg, N(G)()-nitro-L-Arg) and BH(4), together with dithiothreitol (DTT), to the pterin-free ferric low-spin oxygenase domain (gamma(MAX): 419, 538, 568 NM) and incubation for 2-3 days at 4 degrees C converted the domain to a native enzyme-type, predominantly high-spin state (gamma(MAX): approximately 395, approximately 512, approximately 650 NM). 7,8-Dihydrobiopterin and other thiols (E.G., beta-mercaptoethanol, cysteine, and glutathione, with less effectiveness) can replace BH(4) and DTT, respectively. the UV-visible absorption spectrum of L-Arg-bound ferric full length NNOS, which exhibits a relatively intense band at approximately 650 NM (epsilon equals 7.5-8 MM(-)(1) CM(-)(1)) due to the presence of a neutral flavin semiquinone, can then be quantitatively reconstructed by combining the spectra of equimolar amounts of the oxygenase and reductase domains. Of particular note, the heme spin-state conversion does not occur in the absence of a thiol even after prolonged (35-48 H) incubation of the oxygenase domain with BH(4) and/or L-Arg under anaerobic conditions. Thus, DTT (or other thiols) plays a significant role(s) beyond keeping BH(4) in its reduced form, In restoring the pterin- and/or substrate-binding capability of the E. coli-expressed, BH(4) free, dimeric NNOS oxygenase domain. Our results in combination with recently available X-ray crystallography and site-directed mutagenesis data suggest that the observed DTT effects arise from the involvement of an intersubunit disulfide bond or its rearrangement in the NOS dimer.
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Affiliation(s)
- M Sono
- Department of Chemistry and Biochemistry and School of Medicine, University of South Carolina, Columbia, South Carolina 29208, USA.
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6
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Pond AE, Sono M, Elenkova EA, Goodin DB, English AM, Dawson JH. Influence of protein environment on magnetic circular dichroism spectral properties of ferric and ferrous ligand complexes of yeast cytochrome c peroxidase. Biospectroscopy 1999; 5:S42-52. [PMID: 10512537 DOI: 10.1002/(sici)1520-6343(1999)5:5+3.0.co;2-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The addition of exogenous ligands to the ferric and ferrous states of yeast cytochrome c peroxidase (CCP) is investigated with magnetic circular dichroism (MCD) at 4 degrees C to determine the effect the protein environment may exercise on spectral properties. The MCD spectrum of each derivative is directly compared to those of analogous forms of horseradish peroxidase (HRP) and myoglobin (Mb), two well-characterized histidine-ligated heme proteins. The ferric azide adduct of CCP is a hexacoordinate, largely low-spin species with an MCD spectrum very similar to that of ferric azide HRP. This complex displays an MCD spectrum dissimilar from that of the Mb derivative, possibly because of the stabilizing interaction between the azide ligand and the distal arginine of CCP (Arg 48). For the ferric fluoride derivative all three proteins display varied MCD data, indicating that the differences in the distal pocket of each protein influences their respective MCD characteristics. The MCD data for the cyanoferric complexes are similar for all three proteins, demonstrating that a strong field ligand bound in the sixth axial position dominates the MCD characteristics of the derivative. Similarly, the ferric NO complexes of the three proteins show MCD spectra similar in feature position and shape, but vary somewhat in intensity. Reduction of CCP at neutral pH yields a typical pentacoordinate high-spin complex with an MCD spectrum similar to that of deoxyferrous HRP. Formation of the NO and cyanide complexes of ferrous CCP gives derivatives with MCD spectra similar to the analogous forms of HRP and Mb in both feature position and shape. Addition of CO to deoxyferrous CCP results in a ferrous-CO complex with MCD spectral similarity to that of ferrous-CO HRP but not Mb, indicating that interactions between the ligand and the distal residues affects the MCD characteristics. Examination of alkaline (pH 9.7) deoxyferrous CCP indicates that a pH dependent conformational change has occurred, leading to a coordination structure similar to that of ferrous cytochrome b5, a known bis-histidine complex. Exposure of this complex to CO further confirms that a conformational change has taken place in that the MCD spectral characteristics of the resulting complex are similar to those of ferrous-CO Mb but not ferrous-CO HRP.
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Affiliation(s)
- A E Pond
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, USA
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7
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Maekura S, Sono M, Teramura K, Satou T, Furuta T, Yoneda E, Hashimoto S, Kimura M. [Subcutaneous phaeohyphomycosis of the right thumb]. Rinsho Byori 1999; 47:976-9. [PMID: 10590674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Black fungi are a group of fungi that are characterized by the development of a pale brown to black color in the cell walls of their vegetative cells, conidia, or both. A mycotic infection caused by a member of black fungi can be subdivided into three clinical entities: phaeohyphomycosis, chromoblastomycosis, and mycetoma. Phaeohyphomycosis is distinguished from mycetoma by the absence of grain (organized, interwoven mycelial aggregates) formation, and from chromoblastomycosis by the absence of sclerotic bodies (thick-walled muriform cells). Phaeohyphomycosis is a rare disease and has been sporadically reported. In the present report, phaeohyphomycosis of the right thumb of a 72-year-old man was presented. A precipitating trauma of two months earlier at the site was recalled. A solitary mass, 10 mm in diameter, was gradually formed in the palm side of the distal right thumb and finally resected. Histological examination disclosed a solitary granulomatous lesion surrounded by an incomplete fibrous capsule. The lesion mainly involved subcutaneous tissue and was composed of multiple pyogranulomas. Pigmented branched septate hyphae and yeast-like cells were sparsely found in the periphery of the abscess and within histiocytic cells of the granulomas. No sclerotic cells were detected. When pigmentation of black fungi in tissue is as faint as in the present case, Fontana-Masson staining is useful to accentuate the presence of melanin-like pigment of fungal cell walls.
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Affiliation(s)
- S Maekura
- Department of Clinical Pathology, Wakakusa Daiichi Hospital, Higashi-Osaka
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8
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Pond AE, Sono M, Elenkova EA, McRee DE, Goodin DB, English AM, Dawson JH. Magnetic circular dichroism studies of the active site heme coordination sphere of exogenous ligand-free ferric cytochrome c peroxidase from yeast: effects of sample history and pH. J Inorg Biochem 1999; 76:165-74. [PMID: 10605835 DOI: 10.1016/s0162-0134(99)00112-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Electronic absorption and magnetic circular dichroism (MCD) spectroscopic data at 4 degrees C are reported for exogenous ligand-free ferric forms of cytochrome c peroxidase (CCP) in comparison with two other histidine-ligated heme proteins, horseradish peroxidase (HRP) and myoglobin (Mb). In particular, we have examined the ferric states of yeast wild-type CCP (YCCP), CCP (MKT) which is the form of the enzyme that is expressed in and purified from E. coli, and contains Met-Lys-Thr (MKT) at the N-terminus, CCP (MKT) in the presence of 60% glycerol, lyophilized YCCP, and alkaline CCP (MKT). The present study demonstrates that, while having similar electronic absorption spectra, the MCD spectra of ligand-free ferric YCCP and CCP (MKT) are somewhat varied from one another. Detailed spectral analyses reveal that the ferric form of YCCP, characterized by a long wavelength charge transfer (CT) band at 645 nm, exists in a predominantly penta-coordinate state with spectral features similar to those of native ferric HRP rather than ferric Mb (His/water hexa-coordinate). The electronic absorption spectrum of ferric CCP (MKT) is similar to those of the penta-coordinate states of ferric YCCP and ferric HRP including a CT band at 645 nm. However, its MCD spectrum shows a small trough at 583 nm that is absent in the analogous spectra of YCCP and HRP. Instead, this trough is similar to that seen for ferric myoglobin at about 585 nm, and is attributed (following spectral simulations) to a minor contribution (< or = 5%) in the spectrum of CCP (MKT) from a hexa-coordinate low-spin species in the form of a hydroxide-ligated heme. The MCD data indicate that the lyophilized sample of ferric YCCP (lambda CT = 637 nm) contains considerably increased amounts of hexa-coordinate low-spin species including both His/hydroxide and bis-His species. The crystal structure of a spectroscopically similar sample of CCP (MKT) (lambda CT = 637 nm) solved at 2.0 A resolution is consistent with His/hydroxide coordination. Alkaline CCP (pH 9.7) is proposed to exist as a mixture of hexa-coordinate, predominantly low-spin complexes with distal His 52 and hydroxide acting as distal ligands based on MCD spectral comparisons.
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Affiliation(s)
- A E Pond
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, USA
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9
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Ledbetter AP, McMillan K, Roman LJ, Masters BS, Dawson JH, Sono M. Low-temperature stabilization and spectroscopic characterization of the dioxygen complex of the ferrous neuronal nitric oxide synthase oxygenase domain. Biochemistry 1999; 38:8014-21. [PMID: 10387045 DOI: 10.1021/bi990619h] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitric oxide (NO), an intercellular messenger and an immuno-cytotoxic agent, is synthesized by the family of nitric oxide synthases (NOS), which are thiolate-ligated, heme-containing monooxygenases that convert L-Arg to L-citrulline and NO in a tetrahydrobiopterin (BH4)-dependent manner, using NADPH as the electron donor. The dioxygen complex of the ferrous enzyme has been proposed to be a key intermediate in the NOS catalytic cycle. In this study, we have generated a stable ferrous-O2 complex of the oxygenase domain of rat neuronal NOS (nNOS) by bubbling O2 through a solution of the dithionite-reduced enzyme at -30 degrees C in a cryogenic solvent containing 50% ethylene glycol. The most stable dioxygen complex is obtained using the oxygenase domain which has been preincubated for an extended length of time at 4 degrees C with BH4/dithiothreitol and NG-methyl-L-arginine, a substrate analogue inhibitor. The O2 complex of the nNOS oxygenase domain thus prepared exhibits UV-visible absorption (maxima at 419 and 553 nm, shoulder at approximately 585 nm) and magnetic circular dichroism spectra that are nearly identical to those of ferrous-O2 cytochrome P450-CAM. Our spectral data are noticeably blue-shifted from those seen at 10 degrees C for a short-lived transient species (lambdamax = 427 nm) for the nNOS oxygenase domain using stopped-flow rapid-scanning spectroscopy [Abu-Soud, H. M., Gachhui, R., Raushel, F. M., and Stuehr, D. J. (1997) J. Biol. Chem. 272, 17349], but somewhat similar to those of a relatively stable O2 adduct of L-Arg-free full-length nNOS (lambdamax = 415-416.5 nm) generated at -30 degrees C [Bec, N., Gorren, A. C. F., Voelder, C., Mayer, B., and Lange, R. (1998) J. Biol. Chem. 273, 13502]. Compared with ferrous-O2 P450-CAM, however, the ferrous-O2 adduct of the nNOS oxygenase domain is considerably more autoxidizable and the O2-CO exchange reaction is noticeably slower. The generation of a stable ferrous-O2 adduct of the nNOS oxygenase domain, as described herein, will facilitate further mechanistic and spectroscopic investigations of this important intermediate.
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Affiliation(s)
- A P Ledbetter
- Department of Chemistry and Biochemistry, School of Medicine, University of South Carolina, Columbia 29208, USA
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10
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Pond AE, Roach MP, Sono M, Rux AH, Franzen S, Hu R, Thomas MR, Wilks A, Dou Y, Ikeda-Saito M, Ortiz de Montellano PR, Woodruff WH, Boxer SG, Dawson JH. Assignment of the heme axial ligand(s) for the ferric myoglobin (H93G) and heme oxygenase (H25A) cavity mutants as oxygen donors using magnetic circular dichroism. Biochemistry 1999; 38:7601-8. [PMID: 10360958 DOI: 10.1021/bi9825448] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
UV-visible absorption and magnetic circular dichroism (MCD) data are reported for the cavity mutants of sperm whale H93G myoglobin and human H25A heme oxygenase in their ferric states at 4 degreesC. Detailed spectral analyses of H93G myoglobin reveal that its heme coordination structure has a single water ligand at pH 5.0, a single hydroxide ligand at pH 10.0, and a mixture of species at pH 7.0 including five-coordinate hydroxide-bound, and six-coordinate structures. The five-coordinate aquo structure at pH 5 is supported by spectral similarity to acidic horseradish peroxidase (pH 3.1), whose MCD data are reported herein for the first time, and acidic myoglobin (pH 3.4), whose structures have been previously assigned by resonance Raman spectroscopy. The five-coordinate hydroxide structure at pH 10.0 is supported by MCD and resonance Raman data obtained here and by comparison with those of other known five-coordinate oxygen donor complexes. In particular, the MCD spectrum of alkaline ferric H93G myoglobin is strikingly similar to that of ferric tyrosinate-ligated human H93Y myoglobin, whose MCD data are reported herein for the first time, and that of the methoxide adduct of ferric protoporphyrin IX dimethyl ester (FeIIIPPIXDME). Analysis of the spectral data for ferric H25A heme oxygenase at neutral pH in the context of the spectra of other five-coordinate ferric heme complexes with proximal oxygen donor ligands, in particular the p-nitrophenolate and acetate adducts of FeIIIPPIXDME, is most consistent with ligation by a carboxylate group of a nearby glutamyl (or aspartic) acid residue.
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Affiliation(s)
- A E Pond
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, USA
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11
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Sono M, Stuehr DJ, Ikeda-Saito M, Dawson JH. Identification of nitric oxide synthase as a thiolate-ligated heme protein using magnetic circular dichroism spectroscopy. Comparison with cytochrome P-450-CAM and chloroperoxidase. J Biol Chem 1995; 270:19943-8. [PMID: 7544348 DOI: 10.1074/jbc.270.34.19943] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Nitric oxide (NO) has recently been recognized as an important biomolecule playing diverse physiological roles. It is synthesized in several different tissues from L-Arg and O2, using NADPH as an electron donor, by a family of heme-containing catalytically self-sufficient monooxygenases known as nitric oxide synthases (NOS). Recently, the CO complex of reduced NOS has been shown to exhibit an absorption maximum near 450 nm, a characteristic spectral feature of cytochrome P-450 (P-450). Yet, the amino acid sequences of NOS and P-450 have no homology. To further probe the active site heme coordination structure and the heme environment of NOS, we have employed magnetic circular dichroism (MCD) and CD spectroscopy in the present study. MCD spectra of several derivatives of rat brain neuronal NOS strikingly resemble those of analogous derivatives of bacterial P-450-CAM and fungal chloroperoxidase, two known thiolate-ligated heme proteins. Given the proven fingerprinting capability of MCD spectroscopy, this provides convincing evidence for endogenous thiolate (cysteinate) ligation to the heme iron of NOS. Furthermore, the heme-related Soret CD bands of NOS (positive) and P-450s (negative), as represented by P-450-CAM, are almost mirror images, whereas chloroperoxidase exhibits totally different CD band shapes. This suggests that the active sites of NOS and P-450 may share some common structural features, but significant distinctions exist between their heme environments in certain aspects such as hydrophobicity or size.
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Affiliation(s)
- M Sono
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, USA
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12
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Liu HI, Sono M, Kadkhodayan S, Hager LP, Hedman B, Hodgson KO, Dawson JH. X-ray absorption near edge studies of cytochrome P-450-CAM, chloroperoxidase, and myoglobin. Direct evidence for the electron releasing character of a cysteine thiolate proximal ligand. J Biol Chem 1995; 270:10544-50. [PMID: 7737989 DOI: 10.1074/jbc.270.18.10544] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The low spin ferric and low and high spin ferrous forms of myoglobin, bacterial cytochrome P-450-CAM, and chloroperoxidase have been examined by Fe-K x-ray absorption edge spectroscopy. The positions of the absorption edge and the shapes of preedge and edge regions of imidazole adducts of ferric P-450-CAM and chloroperoxidase are essentially the same when compared with thiolate-ligated ferric myoglobin. As these three protein derivatives all have six-coordinate, low spin, ferric hemes with axial imidazole and thiolate ligands, the superposition of x-ray absorption edge spectral properties demonstrates that the protein environment does not effect the spectra, provided one compares heme iron centers with identical coordination numbers, spin and oxidation states, and ligand sets. In contrast, a 0.96 eV difference is observed in the energy of the absorption edge for imidazole- and thiolate-ligated ferric myoglobin with the latter shifted to lower energy as observed for ferrous myoglobin states. Similarly, in the low spin ferric-imidazole and ferrous-CO states, the energies of the absorption edge for chloroperoxidase and P-450-CAM are shifted in the direction of the ferrous state (to lower energy) when compared with those for analogous myoglobin derivatives. In the deoxyferrous high spin state, comparison of the edge spectra of chloroperoxidase with analogous data for cytochrome P-450-CAM suggests that the electron density at the iron is similar for these two protein states. The shifts observed in the energies of the x-ray absorption edge for the thiolate-ligated states of these proteins relative to derivatives lacking a thiolate ligand provide a direct measure of the electron releasing character of a thiolate axial ligand. These results therefore support the suggested role of the cysteinate proximal ligand of P-450 as a strong internal electron donor to promote O-O bond cleavage in the putative ferric-peroxide intermediate to generate the proposed ferryl-oxo "active oxygen" state of the reaction cycle.
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Affiliation(s)
- H I Liu
- Department of Chemistry, Stanford University, California 94305, USA
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13
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Dawson JH, Kadkhodayan S, Zhuang C, Sono M. On the use of iron octa-alkylporphyrins as models for protoporphyrin IX-containing heme systems in studies employing magnetic circular dichroism spectroscopy. J Inorg Biochem 1992; 45:179-92. [PMID: 1634892 DOI: 10.1016/0162-0134(92)80043-u] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The magnetic circular dichroism (MCD) properties of numerous oxidation and ligation state derivatives of myoglobin and horseradish peroxidase reconstituted with an iron octa-alkylporphyrin (mesoheme IX) have been investigated in order to establish the utility of such porphyrins as models for protoporphyrin IX-containing systems. The MCD spectra of the mesoheme-reconstituted proteins are blue-shifted (4-12 nm) and are somewhat more intense (1.5-2.5 fold) when compared to the spectra of analogous derivatives of native myoglobin and horseradish peroxidase. However, the spectral band patterns of the mesoheme-reconstituted proteins closely resemble those of the native proteins in essentially all cases. These data demonstrate that octa-alkylporphyrins can be productively used as models for protoporphyrin IX in studies of heme proteins with MCD spectroscopy.
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Affiliation(s)
- J H Dawson
- Department of Chemistry and Biochemistry, School of Medicine, University of South Carolina, Columbia 29208
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14
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Dawson JH, Bracete AM, Huff AM, Kadkhodayan S, Zeitler CM, Sono M, Chang CK, Loewen PC. The active site structure of E. coli HPII catalase. Evidence favoring coordination of a tyrosinate proximal ligand to the chlorin iron. FEBS Lett 1991; 295:123-6. [PMID: 1662642 DOI: 10.1016/0014-5793(91)81401-s] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
E. coli produces 2 catalases known as HPI and HPII. While the heme prosthetic group of the HPII catalase has been established to be a dihydroporphyrin or chlorin, the identity of the proximal ligand to the iron has not been addressed. The magnetic circular dichroism (MCD) spectrum of native ferric HPII catalase is very similar to those of a 5-coordinate phenolate-ligated ferric chlorin complex, a model for tyrosinate proximal ligation, as well as of chlorin-reconstituted ferric horseradish peroxidase, a model for 5-coordinate histidine ligation. However, further MCD comparisons of chlorin-reconstituted myoglobin with parallel ligand-bound adducts of the catalase clearly rule out histidine ligation in the latter, leaving tyrosinate as the best candidate for the proximal ligand.
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Affiliation(s)
- J H Dawson
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208
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15
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Sono M, Bracete AM, Huff AM, Ikeda-Saito M, Dawson JH. Evidence that a formyl-substituted iron porphyrin is the prosthetic group of myeloperoxidase: magnetic circular dichroism similarity of the peroxidase to Spirographis heme-reconstituted myoglobin. Proc Natl Acad Sci U S A 1991; 88:11148-52. [PMID: 1662385 PMCID: PMC53091 DOI: 10.1073/pnas.88.24.11148] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
To probe the identity of the active site heme-type prosthetic group of myeloperoxidase, whose structure has not been established unambiguously [proposed structures are (i) a chlorin (dihydroporphyrin) or (ii) a formyl-substituted porphyrin such as present in heme a], Spirographis heme (2-formyl-4-vinyldeuteroheme IX) has been incorporated into apo-myoglobin as a possible iron porphyrin model. Comparison of parallel derivatives of these two green proteins with magnetic circular dichroism spectroscopy reveals considerable similarities between several derivatives of these proteins, including the pyridine hemochromogen, the native ferric, ferrous-oxy, and ferrous-CO forms. In contrast, the magnetic circular dichroism spectra of available iron chlorin (octaethylchlorin) model complexes in analogous ligation and oxidation states do not show any significant spectral similarities to myeloperoxidase. This finding provides important evidence in favor of a formyl-substituted porphyrin as the structure of the prosthetic group macrocycle of myeloperoxidase.
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Affiliation(s)
- M Sono
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208
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Cady SG, Sono M. 1-Methyl-DL-tryptophan, beta-(3-benzofuranyl)-DL-alanine (the oxygen analog of tryptophan), and beta-[3-benzo(b)thienyl]-DL-alanine (the sulfur analog of tryptophan) are competitive inhibitors for indoleamine 2,3-dioxygenase. Arch Biochem Biophys 1991; 291:326-33. [PMID: 1952947 DOI: 10.1016/0003-9861(91)90142-6] [Citation(s) in RCA: 238] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
1-methyl-DL-Trp, beta-(3-benzofuranyl)-DL-alanine (the oxygen analog of Trp), and beta-[3-benzo(b)thienyl]-DL-alanine (the sulfur analog of Trp), each of which has a substitution at the indole nitrogen atom, were found to be the first examples of potent substrate analog competitive inhibitors (Ki 7-70 microM) with respect to the substrates D-Trp and L-Trp for rabbit small intestinal indoleamine 2,3-dioxygenase. Binding studies using optical absorption and CD spectroscopy demonstrated that these three inhibitors cause spectral changes upon binding to the native ferric, ferrous, ferrous-CO, and ferrous-NO enzymes. Such spectral effects of 1-methyl-DL-Trp on all of these enzyme derivatives were similar to those caused by L-Trp, while the sulfur and the oxygen analogs of Trp exhibit relatively small effects except for those observed for the sulfur analog with CD spectroscopy. Each of these three Trp analog inhibitors competes with L-Trp for the ferrous-CO enzyme, a model for the ferrous-O2 enzyme. The present findings demonstrate that, although substitution of a methyl group for the hydrogen atom on the indole nitrogen or of a more electron-inductive sulfur or oxygen atom for the indole nitrogen atom does not prevent the binding of the resulting Trp analog to indoleamine 2,3-dioxygenase, the free form of the indole nitrogen base is an important physical and/or electronic structural requirement for Trp to be metabolized by the enzyme. The inability of 1-methyl-Trp to serve as a substrate for the dioxygenase supports a view that singlet oxygen is not the reactive oxygen species involved in the dioxygenation of Trp by the enzyme.
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Affiliation(s)
- S G Cady
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208
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Bracete AM, Sono M, Dawson JH. Effects of cyanogen bromide modification of the distal histidine on the spectroscopic and ligand binding properties of myoglobin: magnetic circular dichroism spectroscopy as a probe of distal water ligation in ferric high-spin histidine-bound heme proteins. Biochim Biophys Acta 1991; 1080:264-70. [PMID: 1954234 DOI: 10.1016/0167-4838(91)90012-o] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Magnetic circular dichroism (MCD) spectroscopy has been utilized to characterize the change in coordination structure in native ferric sperm whale myoglobin upon cyanogen bromide-modification. Comparison of the MCD properties of the ferric high-spin state of cyanogen bromide-modified myoglobin (BrCN-Mb) with those of native ferric horseradish peroxidase and Aplysia myoglobin suggests that ferric BrCN-Mb is a potential MCD model for the pentacoordinate state of ferric high-spin histidine-ligated heme proteins. These five-coordinate heme proteins afford a relatively weak and unsymmetric signal in the Soret region of the MCD spectrum. In contrast, native ferric myoglobin and the benzohydroxamic acid adduct of ferric horseradish peroxidase show a strong and symmetric derivative-shaped Soret MCD signal which is indicative of hexacoordination with water and histidine axial ligands. Therefore it seems that MCD spectroscopy could be used to probe the presence of water ligated to the distal side of ferric high-spin heme proteins. The MCD spectra of the ferric-azide, ferrous-deoxy and ferrous-CO forms of BrCN-Mb have also been measured and compared to those of analogous native myoglobin complexes. The present MCD study has been extended to include new ligands, NO, thiocyanate and cyanate, which bind to ferric BrCN-Mb. With exogenous ligands such as CO, NO and thiocyanate, the coordination structures of the BrCN-Mb complexes are similar to those of the respective native myoglobin adducts. In the case of ferrous-deoxy and ferric-cyanate BrCN-Mb, however, the altered MCD spectra (and EPR for the latter) reveal changes in electronic structure which likely correlate with alterations of the coordination environment of these BrCN-Mb derivatives. Data are also presented which support the proposed tetrazole-bound structure for azide-treated BrCN-Mb (Hori, H., Fujii, M., Shiro, Y., Iizuka, T., Adachi, S. and Morishima, I. (1989) J. Biol. Chem. 264, 5715-5719) and the inability of the distal histidine of BrCN-Mb to stabilize the ferric ligand-bound state.
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Affiliation(s)
- A M Bracete
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208
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Crull G, Wong H, Sono M. Initial investigations of the active site of the heme protein indoleamine 2,3-dioxygenase (IDO): Evidence for the interaction of water with the active site from proton NMR. J Inorg Biochem 1991. [DOI: 10.1016/0162-0134(91)84294-j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Sono M, Hager LP, Dawson JH. Electron paramagnetic resonance investigations of exogenous ligand complexes of low-spin ferric chloroperoxidase: further support for endogenous thiolate ligation to the heme iron. Biochim Biophys Acta 1991; 1078:351-9. [PMID: 1650250 DOI: 10.1016/0167-4838(91)90156-t] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Previous spectroscopic studies of chloroperoxidase have provided evidence for endogenous thiolate sulfur donor ligation to the central heme iron of the enzyme. This conclusion is further supported by recent DNA sequence data which revealed the existence of a third cysteine residue (in addition to a disulfide pair detected earlier) in the protein available for coordination to the heme iron. Thus, chloroperoxidase shares many spectroscopic properties with cytochrome P-450, the only other known thiolate-ligated heme protein. Surprisingly, a previous electron paramagnetic resonance (EPR) study of low-spin ferric chloroperoxidase-ligand complexes (Hollenberg, P.F., Hager, L.P., Blumberg, W.E. and Peisach, J. (1980) J. Biol. Chem. 255, 4801-4807) was unable to provide clear support for the presence of a thiolate ligand, although sulfur coordination was implicated. This was, in part, because an insufficient number of complexes was examined. In this work, we have significantly expanded upon the previous EPR study by using an extensive variety of over twenty exogenous ligands including carbon, nitrogen, oxygen, phosphorus and sulfur donors. Crystal field analysis, using the procedure of Blumberg and Peisach, of the present data in comparison with data for analogous complexes of cytochrome P-450-CAM, thiolate-ligated heme model systems, and myoglobin, is clearly indicative of endogenous thiolate ligation for chloroperoxidase. In addition, the UV-visible absorption and EPR spectral data suggest that a carboxylate ligand is a possible candidate for the endogenous sixth ligand to the heme iron that is responsible for the reversible conversion of ferric chloroperoxidase from high-spin to low-spin at low temperatures (less than 200 K).
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Affiliation(s)
- M Sono
- Department of Chemistry, University of South Carolina, Columbia 29208
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Abstract
The binding of a number of ligands to the heme protein indolamine 2,3-dioxygenase has been examined with UV-visible absorption and with natural and magnetic circular dichroism spectroscopy. Relatively large ligands (e.g., norharman) which do not readily form complexes with myoglobin and horseradish peroxidase (HRP) can bind to the dioxygenase. Except for only a few cases (e.g., 4-phenylimidazole) for the ferric dioxygenase, a direct competition for the enzyme rarely occurs between the substrate L-tryptophan (Trp) and the ligands examined. L-Trp and small heme ligands (CN-,N3-,F-) markedly enhance the affinity of each other for the ferric enzyme in a reciprocal manner, exhibiting positive cooperativity. For the ferrous enzyme, L-Trp exerts negative cooperativity with some ligands such as imidazoles, alkyl isocyanides, and CO binding to the enzyme. This likely reflects the proximity of the Trp binding site to the heme iron. Other indolamine substrates also exert similar but smaller cooperative effects on the binding of azide or ethyl isocyanide. The pH dependence of the ligand affinity of the dioxygenase is similar to that of myoglobin rather than that of HRP. These results suggest that indolamine 2,3-dioxygenase has the active-site heme pocket whose environmental structure is similar to, but whose size is considerably larger than, that of myoglobin, a typical O2-binding heme protein. Although the L-Trp affinity of the ferric cyanide and ferrous CO enzyme varies only slightly between pH 5.5 and 9.5, the unligated ferric and ferrous enzymes have considerably higher affinity for L-Trp at alkaline pH than at acidic pH. L-Trp binding to the ferrous dioxygenase is affected by an ionizable residue with a pKa value of 7.3.
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Affiliation(s)
- M Sono
- Department of Chemistry, University of South Carolina, Columbia 29208
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Kobayashi K, Hayashi K, Sono M. Effects of tryptophan and pH on the kinetics of superoxide radical binding to indoleamine 2,3-dioxygenase studied by pulse radiolysis. J Biol Chem 1989; 264:15280-3. [PMID: 2549057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The reaction of superoxide radical (O2-) with the heme protein indoleamine 2,3-dioxygenase has been investigated by the use of pulse radiolysis. In the absence of the substrate tryptophan (Trp), the ferric enzyme reacted quantitatively with O2- to form the oxygenated enzyme. The rate constant for the reaction (8.0 x 10(6) M-1 s-1 at pH 7.0) increased with a decrease in pH. In the presence of low concentrations of L-Trp (approximately 50 microM), under which the catalytic site of the ferric enzyme is greater than 99% Trp-free at pH 7.0, the only spectral species observed upon O2- binding was L-Trp-bound oxygenated enzyme, the ternary complex. This suggests that under the conditions employed O2- binds first to the ferric enzyme to form the oxygenated enzyme and is followed by rapid binding of L-Trp. It was also found that absorbance changes (delta A) for the enzyme after the pulse were significantly decreased when an increased L-Trp concentration was employed. A 50% decrease in delta A was caused with approximately 50 microM L-Trp at pH 7.0. Similar results were also observed with other indole derivatives with decreasing delta A values in the order of indole, 3-indoleethanol, alpha-methyl-DL-Trp, and D-Trp. These results suggest that there exists a binding site for these compounds in the dioxygenase different from the catalytic site for Trp and, most significantly, that binding of Trp to the effector binding site of the ferric enzyme markedly inhibits its reaction with O2-.
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Affiliation(s)
- K Kobayashi
- Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Japan
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Kobayashi K, Hayashi K, Sono M. Effects of tryptophan and pH on the kinetics of superoxide radical binding to indoleamine 2,3-dioxygenase studied by pulse radiolysis. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84822-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Sono M, Kobayashi K, Hayashi K. A pulse radiolysis study of the reaction of superoxide anion (O2⨪) with the heme protein indoleamine 2,3-dioxygenase (IDO). J Inorg Biochem 1989. [DOI: 10.1016/0162-0134(89)84493-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Sono M. Enzyme kinetic and spectroscopic studies of inhibitor and effector interactions with indoleamine 2,3-dioxygenase. 2. Evidence for the existence of another binding site in the enzyme for indole derivative effectors. Biochemistry 1989; 28:5400-7. [PMID: 2789077 DOI: 10.1021/bi00439a013] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
To probe the active site of the heme protein indoleamine 2,3-dioxygenase, the effects of 3-indoleethanol (IET) (or tryptophol), one of the known indole derivative effectors, and indole (IND) on the catalytic (Vmax, Km) and spectroscopic properties (optical absorption and CD) of the enzyme were investigated. Assays were performed with the substrate L- or D-tryptophan (Trp) and an ascorbic acid-methylene blue cofactor system at 25 degrees C. This study has shown that, at millimolar concentrations, both IET and IND lower considerably the Km value for D-Trp by approximately 25% and approximately 60%, respectively, at pH 7.0, while neither affects the Km value for L-Trp. Interestingly, however, these effectors exert opposite effects with respect to each other on the Vmax values for both D-Trp and L-Trp: IET enhances the Vmax values by 40-60% while IND lowers them by 12-24%. These effects of IET and IND on the Vmax values may be attributed to the shift in the ferric (inactive) enzyme----ferrous (active) enzyme equilibrium either to the right (IET) or to the left (IND) caused by the binding of these effectors to the enzyme in the steady state of the catalytic reaction. Both effectors induce clearly detectable spectral changes, especially notable in CD spectra, upon binding (in a 1:1 molar ratio, Kd = 10(-4) to 2.5 X 10(-3) M) to the ferrous enzyme and its complexes with O2, CO, and NO, both in the presence and in the absence of L-Trp.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Sono
- Department of Chemistry, University of South Carolina, Columbia 29208
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Sono M, Cady SG. Enzyme kinetic and spectroscopic studies of inhibitor and effector interactions with indoleamine 2,3-dioxygenase. 1. Norharman and 4-phenylimidazole binding to the enzyme as inhibitors and heme ligands. Biochemistry 1989; 28:5392-9. [PMID: 2789076 DOI: 10.1021/bi00439a012] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of norharman, one of the few known inhibitors of the heme protein indoleamine 2,3-dioxygenase, and of 4-phenylimidazole (4-PheImid), a heme ligand, on the catalytic (Vmax, Km) and spectroscopic properties (optical absorption, CD, and magnetic CD) of the rabbit small intestinal dioxygenase were investigated. Assays were performed with the substrate L- or D-tryptophan (Trp) and an ascorbic acid-methylene blue cofactor system at 25 degrees C. This study has revealed that both norharman and 4-PheImid exhibit noncompetitive inhibition with respect to L-Trp and D-Trp. The binding of norharman to the enzyme results in the formation of a low-spin complex in both the ferric and ferrous enzyme with comparable dissociation constants (Kd = approximately 10 microM at pH 7.0) that are about 10 times smaller than the observed Ki value. L-Trp exerts no effect for the ferric enzyme and slight negative cooperative effects for the ferrous enzyme on norharman binding. Close spectral similarities are observed between the adducts of the enzyme with norharman and 4-PheImid in the respective oxidation states. This, together with competition experiments using cyanide, demonstrates that norharman binds directly to the heme iron of the enzyme as a nitrogen donor ligand. Thus, norharman competes with O2 for the heme iron of the ferrous (active) enzyme, resulting in the observed inhibition. L-Trp and 4-PheImid appear to compete for the heme binding site in the ferric enzyme and display slight negative cooperativity on binding to the ferrous enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Sono
- Department of Chemistry, University of South Carolina, Columbia 29208
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Sono M. The roles of superoxide anion and methylene blue in the reductive activation of indoleamine 2,3-dioxygenase by ascorbic acid or by xanthine oxidase-hypoxanthine. J Biol Chem 1989; 264:1616-22. [PMID: 2536368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
To clarify the roles of superoxide anion (O2.-) and methylene blue in the reductive activation of the heme protein indoleamine 2,3-dioxygenase, effects of xanthine oxidase-hypoxanthine used at various oxidase concentration levels as an O2.- source and an electron donor on the catalytic activity of the dioxygenase have been examined in the presence and absence of either methylene blue or superoxide dismutase using L- and D-tryptophan as substrates. In the absence of methylene blue, initial rates of the product N-formylkynurenine formation are enhanced in parallel with the xanthine oxidase level up to approximately 100 and approximately 50% of the apparent maximal activity (approximately 2 s-1) for L- and D-Trp, respectively. Superoxide dismutase effectively inhibits the reactions by 80-98% for both isomers. Additions of methylene blue (25 microM) help to maintain the linearity of the product formation that would be rapidly lost a few minutes after the start of the reaction without the dye, especially for L-Trp. Additions of methylene blue also enhance the activity to the maximal level for D-Trp. In the presence of methylene blue, the inhibitory effects of superoxide dismutase are considerably decreased with the increase in xanthine oxidase concentration, and at near maximal dioxygenase activity levels superoxide dismutase is totally without effect. In separate anaerobic experiments leuco-methylene blue, generated either by photoreduction or by ascorbate reduction, is shown to be able to reduce the ferric dioxygenase up to 25-40%. Substrate Trp and heme ligands (CO, n-butyl isocyanide) help to shift a ferric form----ferrous form equilibrium to the right. Thus, under aerobic conditions leuco-methylene blue might similarly be able to reduce the dioxygenase in the presence of an electron donor with the aid of substrate and O2. These results strongly suggest that indoleamine 2,3-dioxygenase can be activated through different pathways either by O2.- or by an electron donor-methylene blue system. For the latter case, the dye is acting as an electron mediator from the donor to the ferric dioxygenase.
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Affiliation(s)
- M Sono
- Department of Chemistry, University of South Carolina, Columbia, 29208
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Sono M. Spectroscopic and equilibrium properties of the indoleamine 2,3-dioxygenase-tryptophan-O2 ternary complex and of analogous enzyme derivatives. Tryptophan binding to ferrous enzyme adducts with dioxygen, nitric oxide, and carbon monoxide. Biochemistry 1986; 25:6089-97. [PMID: 3098285 DOI: 10.1021/bi00368a038] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The dioxygen adduct of the heme protein indoleamine 2,3-dioxygenase has been generated at -30 degrees C in mixed solvents, and spectroscopic and equilibrium studies of its L-tryptophan (substrate) binding properties have been carried out for the first time. Comparative studies have also been performed with the NO and CO adducts of the ferrous enzyme. Under the conditions employed (-30 degrees C), both autoxidation and turnover (L-tryptophan + O2----formylkynurenine) of the ternary complex are effectively suppressed. Structural identification of the ternary complex is based on the 1:1 molar stoichiometry for the substrate-oxygenated enzyme adduct formation (Kd approximately 10(-4) M), the time-dependent linear product formation (turnover) at -20 degrees C, and the quantitative conversion of the complex to the ferrous CO derivative by bubbling with CO. Binding of L-tryptophan to the oxygenated enzyme leads to decreases in the intensities of its major absorption bands (lambda max 415, 541, 576 nm) and to a blue shift of its Soret peak. Interestingly, among the ferrous enzyme derivatives examined, only the substrate-bound oxygenated enzyme exhibits solvent-dependent Soret absorption peak positions, e.g., lambda max 411.5 and 413.5 nm in 65% (v/v) aqueous glycerol and ethylene glycol, respectively. In addition, indole binds to the oxygenated enzyme, causing a red shift of its Soret peak in these solvents only in the presence of substrate (411.5----414 nm and 413.5----414.5 nm, respectively), while similar effects of indole are independent of tryptophan for the other ferrous enzyme derivatives.(ABSTRACT TRUNCATED AT 250 WORDS)
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Sono M, Dawson JH, Ikeda-Saito M. Characterization of the spleen green hemeprotein with magnetic and natural circular dichroism spectroscopy: positive evidence for a myeloperoxidase-type active site. Biochim Biophys Acta 1986; 873:62-72. [PMID: 3017435 DOI: 10.1016/0167-4838(86)90190-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The green hemeprotein purified from bovine spleen has been characterized with magnetic and natural circular dichroism (MCD and CD) spectroscopy for the first time. The enzyme derivatives studied include the native high-spin ferric form and its high-spin chloride and low-spin cyanide and nitrite complexes, the ligand-free high-spin ferrous form and its low-spin CO adduct, and Compounds II (ferryl iron species) and III (dioxygen adduct). All these enzyme states exhibit MCD spectra that are considerably different from the spectra of analogous complexes of normal heme iron. In particular, the following distinctions have been observed. The sign of the derivative-shaped MCD bands of the high-spin ferric and Compound II forms in the Soret (380-500 nm) region and of the ferrous low-spin and Compound III forms in both the Soret and visible (500-700 nm) regions are opposite to and, except for the high-spin ferric form, are less symmetric than those seen for normal heme iron systems. MCD intensities in the Soret region for the high-spin ferrous and low-spin ferric derivatives are noticeably smaller than those of normal heme proteins by a factor of up to ten. Prominent MCD bands are seen around 450 and 630 nm for the green hemeprotein derivatives; these features are considerably red-shifted (30-50 nm) relative to the analogous transitions observed for normal heme proteins. In contrast to the aforementioned spectral differences, the MCD and CD spectra of the spleen green hemeprotein derivatives are essentially identical to those previously reported for several derivatives of another spectroscopically anomalous heme-type enzyme, myeloperoxidase. This provides strong evidence that the two enzymes have identical prosthetic groups and endogenous axial ligands coordinated to the central iron. The novel MCD features of the green proteins, taken together with previously reported spectroscopic results, are most consistent with the presence of a chlorin-type prosthetic group in both proteins. In addition, the CD spectral similarities suggest that the two green proteins have nearly identical active-site environments.
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Sono M, Dawson JH, Hall K, Hager LP. Ligand and halide binding properties of chloroperoxidase: peroxidase-type active site heme environment with cytochrome P-450 type endogenous axial ligand and spectroscopic properties. Biochemistry 1986; 25:347-56. [PMID: 3955002 DOI: 10.1021/bi00350a011] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Equilibrium binding studies of exogenous ligands and halides to the active site heme iron of chloroperoxidase have been carried out from pH 2 to 7. Over twenty ligands have been studied including C, N, O, P, and S donors and the four halides. As judged from changes in the optical absorption spectra, direct binding of the ligands to the heme iron of ferric or ferrous chloroperoxidase occurs in all cases; this has been ascertained for the ferric enzyme in several cases through competition experiments with cyanide. All of the ligands except for the halides, nitrate, and acetate form exclusively low-spin complexes in analogy to results obtained with the spectroscopically related protein, cytochrome P-450-CAM [Sono, M., & Dawson, J.H. (1982) J. Biol. Chem. 257, 5496-5502]. The titration results show that, for the ferric enzyme, (i) weakly acidic ligands (pKa greater than 3) bind to the enzyme in their neutral (protonated) form, followed by deprotonation upon ligation to the heme iron. In contrast, (ii) strongly acidic ligands (pKa less than 0) including SCN-, NO3-, and the halides except for F- likely bind in their anionic (deprotonated) form to the acid form of the enzyme: a single ionizable group on the protein with a pKa less than 2 is involved in this binding. For the ferrous enzyme, (iii) a single ionizable group with the pKa value of 5.5 affects ligand binding. These results reveal that chloroperoxidase, in spite of the previously established close spectroscopic and heme iron coordination structure similarities to the P-450 enzymes, clearly belongs to the hydroperoxidases in terms of its ligand binding properties and active site heme environment. Magnetic circular dichroism studies indicate that the alkaline form (pH 9.5) of ferric chloroperoxidase has an RS-ferric heme-N donor ligand coordination structure with the N donor likely derived from histidine imidazole.
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Sono M, Eble KS, Dawson JH, Hager LP. Preparation and properties of ferrous chloroperoxidase complexes with dioxygen, nitric oxide, and an alkyl isocyanide. Spectroscopic dissimilarities between the oxygenated forms of chloroperoxidase and cytochrome P-450. J Biol Chem 1985; 260:15530-5. [PMID: 2999120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Extensive spectroscopic investigations of chloroperoxidase and cytochrome P-450 have consistently revealed close similarities between these two functionally distinct enzymes. Although the CO-bound ferrous states were the first to display such resemblance, additional comparisons have focused on the native ferric and ferrous and the ligand-bound ferric derivatives of the enzymes. In order to test the extent to which the spectral properties of the two enzymes match each other, we have prepared the NO, alkyl isocyanide, and O2 adducts of ferrous chloroperoxidase, the latter two for the first time. As expected, the NO adducts of the two proteins have similar UV-visible absorption and magnetic circular dichroism spectra; the same behavior is observed for the alkyl isocyanide complexes. Unexpectedly, the dioxygen adduct of ferrous chloroperoxidase (i.e. Compound III), generated in cryogenic solvents at -30 degrees C by bubbling with O2, is spectrally distinct from oxy-P-450-CAM. Identification of this derivative as oxygenated chloroperoxidase is based on the following criteria: It is EPR-silent at 77 K. The bound O2 is dissociable as judged by the uniform conversion to the CO-bound form. Oxy-chloroperoxidase autoxidizes to form the native ferric enzyme without detectable intermediates at a rate comparable to that determined for oxy-P-450-CAM. Oxy-chloroperoxidase exhibits optical absorption (lambda nm (epsilon mM) = 354 (41), 430 (94), 554 (16.5), 587 (12.5)) and magnetic circular dichroism spectra that are clearly distinct from those of histidine-ligated heme proteins such as oxy-myoglobin or oxy-horseradish peroxidase. Surprisingly, several of its spectral properties, namely the red-shifted Soret peak and discrete alpha peak, are also unlike those of oxy-P-450-CAM. Since considerable evidence has accumulated supporting the ligation of an endogenous thiolate to the heme iron of chloroperoxidase, as has been established for the P-450 enzyme, the observed dissimilarities suggest that the electronic properties of the two dioxygen adducts are quite sensitive to differences in their active site heme environment. This, in turn may be related to the functional differences between the two enzymes.
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Sono M, Eble KS, Dawson JH, Hager LP. Preparation and properties of ferrous chloroperoxidase complexes with dioxygen, nitric oxide, and an alkyl isocyanide. Spectroscopic dissimilarities between the oxygenated forms of chloroperoxidase and cytochrome P-450. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)36288-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Sono M, Dawson JH, Hager LP. The generation of a hyperporphyrin spectrum upon thiol binding to ferric chloroperoxidase. Further evidence of endogenous thiolate ligation to the ferric enzyme. J Biol Chem 1984; 259:13209-16. [PMID: 6541651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023] Open
Abstract
In spite of numerous spectroscopic similarities between chloroperoxidase and cytochrome P-450 (P-450) which suggest endogenous cysteinate axial ligation in chloroperoxidase as has been established for P-450, assignment of the endogenous axial ligand of chloroperoxidase has remained controversial since no available free sulfhydryl groups have been detected in chemical studies of chloroperoxidase. To help clarify this problem, we have carried out extensive studies of thiol-binding properties of native ferric chloroperoxidase and have compared our new results with those previously obtained in our laboratory on thiol adducts of P-450. We have found that the ligation of exogenous thiols to the heme iron of chloroperoxidase generates hyperporphyrin (split Soret) spectra (lambda max = approximately 372 and approximately 455 nm), consistent with the formation of bisthiolate low-spin ferric heme adducts as has been established for P-450 and its heme models. However, in contrast to the results with P-450, thiols not only coordinate to the ferric heme iron of chloroperoxidase in the thiolate form in competition with cyanide but also bind, presumably in the thiol form, to a site in the heme vicinity other than the heme iron without competition with cyanide. The thiol acidity (pK alpha greater than 7) or medium pH (pH 3-7) have little effect on the spectral and equilibrium properties of the adducts. Thiol binding to the latter site, which is presumably the organic substrate-binding site, causes a red shift of the Soret peak (339 vector approximately 420 nm) of the high-spin ferric enzyme; the resulting thiol adducts are still predominantly high spin. Similar spectral changes are also observed upon binding of other neutral sulfur (sulfides and disulfide) and oxygen (alcohols and ketones) donor ligands to native ferric chloroperoxidase. In conclusion, the generation of hyperporphyrin spectra upon exogenous thiol binding to native ferric chloroperoxidase provides considerable support for the presence of an endogenous thiolate ligand to the heme of the enzyme in its ferric state.
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Sono M, Dawson JH, Hager LP. The generation of a hyperporphyrin spectrum upon thiol binding to ferric chloroperoxidase. Further evidence of endogenous thiolate ligation to the ferric enzyme. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(18)90679-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Sono M, Dawson JH. Extensive studies of the heme coordination structure of indoleamine 2,3-dioxygenase and of tryptophan binding with magnetic and natural circular dichroism and electron paramagnetic resonance spectroscopy. Biochim Biophys Acta 1984; 789:170-87. [PMID: 6089893 DOI: 10.1016/0167-4838(84)90202-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
In order to probe the active site of the heme protein indoleamine 2,3-dioxygenase, magnetic and natural circular dichroism (MCD and CD) and electron paramagnetic resonance (EPR) studies of the substrate (L-tryptophan)-free and substrate-bound enzyme with and without various exogenous ligands have been carried out. The MCD spectra of the ferric and ferrous derivatives are similar to those of the analogous myoglobin and horseradish peroxidase species. This provides strong support for histidine imidazole as the fifth ligand to the heme iron of indoleamine 2,3-dioxygenase. The substrate-free native ferric enzyme exhibits predominantly high-spin EPR signals (g perpendicular = 6, g parallel = 2) along with weak low-spin signals (g perpendicular = 2.86, 2.28, 1.60); similar EPR, spin-state and MCD features are found for the benzimidazole adduct of ferric myoglobin. This suggests that the substrate-free ferric enzyme has a sterically hindered histidine imidazole nitrogen donor sixth ligand. Upon substrate binding, noticeable MCD and EPR spectral changes are detected that are indicative of an increased low spin content (from 30 to over 70% at ambient temperature). Concomitantly, new low spin EPR signals (g = 2.53, 2.18, 1.86) and MCD features characteristic of hydroxide complexes of histidine-ligated heme proteins appear. For almost all of the other ferric and ferrous derivatives, only small substrate effects are observed with MCD spectroscopy, while substantial substrate effects are seen with CD spectroscopy. Thus, changes in the heme coordination structure of the ferric enzyme and in the protein conformation at the active site of the ferric and ferrous enzyme are induced by substrate binding. The observed substrate effects on the ferric enzyme may correlate with the previously observed kinetic substrate inhibition of indoleamine 2,3-dioxygenase activity, while such effects on the ferrous enzyme suggest the possibility that the substrate is activated during turnover.
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Dawson JH, Andersson LA, Sono M. The diverse spectroscopic properties of ferrous cytochrome P-450-CAM ligand complexes. J Biol Chem 1983; 258:13637-45. [PMID: 6643443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The UV-visible absorption, magnetic circular dichroism (MCD) and CD spectral characteristics of a variety of low spin ferrous P-450-ligand complexes have been carefully determined in order to establish whether all such complexes are hyperporphyrins as previously suggested in the literature. Two general spectral classes are found to occur. Complexes in the first class are, indeed, hyperporphyrin in nature, with pi-acceptor ligands such as CO, NO, phosphine, nitrosoalkanes and isocyanides trans to cysteinate. Individual, but minor, variations in the spectral properties of the hyperporphyrins suggest that subclasses exist, wherein the nature of the trans ligand to thiolate affects the orbital overlap pattern and thus the observed spectra. Adducts in the second spectral class, which have sigma-donor nitrogen and sulfur ligands, also have the red-shifted Soret absorption maximum but are spectrally distinct in all other respects from the hyperporphyrins. Comparison of the MCD spectra of the second category to those of ferrous cytochromes b5, c, and P-420 suggests that the axial cysteinate ligand is still present in the nonhyper ferrous P-450 species. Thus, the combination of a strongly electron-donating cysteinate ligand and a trans sigma-donor, not the orbital mixing mechanism, is most likely the origin of the red-shifted Soret absorption maximum of nonhyper ferrous P-450 ligand complexes. Further, the nature of the total electronic interactions between both axial ligands and the heme iron of ferrous P-450 and not solely the cysteinate ligand determines whether the ligand complexes will be of the hyper or nonhyperporphyrin category. These findings are strengthened by the simultaneous use of three different spectroscopic techniques; together they provide a more detailed explanation for the unusual spectroscopic properties of cytochrome P-450.
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Abstract
Circular dichroism (CD) spectroscopy has been used to probe the active site of bacterial ferric cytochrome P-450CAM. The endogenous sixth ligand to the heme iron has been displaced by an extensive series of exogenous oxygen, nitrogen, sulfur and other neutral and anionic donor ligands in an attempt to examine systematically the steric and electronic factors that influence the coupling of the heme chromophore to its protein environment. General trends for each ligand class are reported and discussed. Both the wavelengths and the intensities of the CD bands vary with ligand type and structure. All but one of the complexes exhibit negative CD maxima in their delta and Soret bands. Comparison to ferric myoglobin-thiolate complexes indicates that the negative sign observed for the cytochrome P-450 spectra is not a property of the thiolate fifth ligand, but rather arises from a different interaction of the cytochrome P-450 heme with its protein environment. Complexes with neutral oxygen donors display CD spectra that most closely resemble the spectrum of the native low-spin enzyme. Hyperporphyrin (split Soret) cytochrome P-450 complexes with thiolates, phosphines and cyanide trans to cysteinate have complex CD spectra, reflecting the intrinsic non-degeneracy of the Soret pi pi transitions. The extensive work presented herein provides an empirical foundation for use in analyzing the interaction of heme chromophores with their protein surroundings, not only for the cytochrome P-450 monooxygenases but also for heme proteins in general.
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Sono M, Andersson LA, Dawson JH. Sulfur donor ligand binding to ferric cytochrome P-450-CAM and myoglobin. Ultraviolet-visible absorption, magnetic circular dichroism, and electron paramagnetic resonance spectroscopic investigation of the complexes. J Biol Chem 1982; 257:8308-20. [PMID: 6282878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The binding of thiol, thiolate, thioether, and disulfide sulfur donor ligands to ferric cytochrome P-450-CAM and myoglobin has been investigated by UV-visible absorption, magnetic circular dichroism (MCD), and EPR spectroscopy. For ferric P-450, the binding of all sulfur donors is competitive with substrate binding. Addition of thiols to P-450 leads to interconvertible thiol or thiolate-bound species depending on the thiol acidity (pKa) and the solution ph; ligation of thiols lowers their pKa by about 4 units. In contrast, only the thiolate-bound form is seen for myoglobin regardless of thiol acidity or solution pH (5.5-11.0), indicating that the heme iron of myoglobin is less electron-rich than that of P-450. Thiolate ligands show much higher affinity (Kd approximately 10(-6) M) for ferric P-450 than do thiols (Kd approximately 10(-3) M). The affinity of thioethers for P-450 (Kd approximately 10(-3) M) is pH-independent (pH 5.5-9.0). The observed disulfide coordination to P-450 represents the first example of disulfide ligation to heme iron; no significant evidence for thioether or disulfide binding to myoglobin is seen. Except for the thiolate complexes, the UV-visible and MCD spectral properties of the other sulfur donor . P-450 complexes are similar to, although distinguishable from, those of native P-450. The ferric P-450 . thiolate complexes exhibit MCD spectra resembling that of ferrous P-450 . CO; both also exhibit unique hyperporphyrin (split Soret) UV-visible spectra. The EPR spectra of all P-450 complexes examined display very narrow spread g-values such as are characteristic of native P-450, indicating that the endogenous cysteinate axial ligand is retained upon complex formation. The dissimilarities observed between P-450 and myoglobin in their reactivity toward sulfur donor ligands at least partly reflect the variation in heme iron electron density resulting from their different endogenous axial ligands and may, in turn, help to explain their respective physiological functions of oxygen activation and reversible oxygen binding.
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Sono M, Andersson LA, Dawson JH. Sulfur donor ligand binding to ferric cytochrome P-450-CAM and myoglobin. Ultraviolet-visible absorption, magnetic circular dichroism, and electron paramagnetic resonance spectroscopic investigation of the complexes. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34332-1] [Citation(s) in RCA: 69] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Sono M, Dawson JH. Formation of low spin complexes of ferric cytochrome P-450-CAM with anionic ligands. Spin state and ligand affinity comparison to myoglobin. J Biol Chem 1982; 257:5496-502. [PMID: 6279603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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Sono M, Dawson JH. Formation of low spin complexes of ferric cytochrome P-450-CAM with anionic ligands. Spin state and ligand affinity comparison to myoglobin. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(19)83805-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Dawson JH, Andersson LA, Sono M. Spectroscopic investigations of ferric cytochrome P-450-CAM ligand complexes. Identification of the ligand trans to cysteinate in the native enzyme. J Biol Chem 1982; 257:3606-17. [PMID: 6277939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
An extensive series of ligand complexes of ferric cytochrome P-450-CAM has been examined by UV-visible absorption, magnetic circular dichroism, and electron paramagnetic resonance spectroscopy in an attempt to identify the ligand trans to cysteinate in the six-coordinate resting state of the enzyme. Thus, the ligands used have been chosen to serve as models for coordination by potential endogenous amino acids and include alcohol, amide and carboxylate oxygen donors, amine, imidazole and indole nitrogen donors and disulfide, thioether, thiol, and thiolate sulfur donors. As this investigation has been by nature an empirical one, the conclusions are strengthened by the concurrent use of three different spectroscopic techniques. All of the complexes formed except those resulting from thiolate addition display spectroscopic properties that are broadly similar to those of low spin, six-coordinate P-450. Of the sulfur donor adducts, disulfide and thioether-bound P-450 have properties that are different enough in detail to distinguish them from native P-450. While the spectral features of the thiol-bound species and of low spin ferric P-450 are alike, the former are pH dependent due to interconversion to bound thiolate, whereas the latter display essentially no spectral changes with pH. Of the oxygen donor complexes, all but carboxylate have spectra that very closely match those of the resting enzyme. Adducts formed with most nitrogenous ligands, including several imidazole derivatives, exhibit spectra that are sufficiently different from native P-450 to exclude them as candidates for the sixth ligand. Interestingly, the spectral properties of a complex formed with an imidazole derivative having a bulky electron-withdrawing substituent in the alpha position are comparable to those native P-450 except for the line shape of the EPR spectrum. Previously published theoretical work suggests that the spectral differences seen between this imidazole derivative and the other examined are electronic and not steric in origin. As no similar electronic mechanism exists for the protein to reduce the electron-donating ability or histidine, it is felt that coordination of histidine in the sixth position of P-450 can be ruled out. In conclusion, close examination of all spectral data reveals that amino acid analog adducts of P-450-CAM with amides and, in particular, alcohols, produce spectra that almost exactly duplicate those of native P-450 and suggests that the ligand trans to cysteinate in the six-coordinate ferric enzyme has an oxygen donor atom.
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Dawson JH, Andersson LA, Sono M. Spectroscopic investigations of ferric cytochrome P-450-CAM ligand complexes. Identification of the ligand trans to cysteinate in the native enzyme. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)34823-3] [Citation(s) in RCA: 208] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Watanabe Y, Yoshida R, Sono M, Hayaishi O. Immunohistochemical localization of indoleamine 2,3-dioxygenase in the argyrophilic cells of rabbit duodenum and thyroid gland. J Histochem Cytochem 1981; 29:623-32. [PMID: 6788834 DOI: 10.1177/29.5.6788834] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
To identify the cells containing indoleamine 2,3-dioxygenase, indirect immunofluorescence studies were performed using the monospecific antibody toward the enzyme purified to apparent homogeneity from rabbit small intestine. The antibody precipitated almost 100% of the enzyme activities of various organs or rabbit in a quantitatively similar manner, but did not cross-react with tryptophan 2,3-dioxygenase [L-tryptophan:oxygen 2,3-oxidoreductase (decyclizing), E.C. 1.13.11.11] in the liver. Immunohistochemical localization was studied using rabbit tissue because of the species-specific reactivity of the antibody. In the duodenum, indoleamine 2,3-dioxygenase-immunoreactive cels were found to be sporadically but exclusively localized in the mucosa, a large number being in the basal portion. No staining was seen in the consecutive sections treated with control immunoglobulin. Restaining within the same section using Grimelius' silver technique revealed that the immunoreactive cells coincided with the argyrophilic cells reportedly containing serotonin under physiological conditions. In the thyroid gland, the immunofluorescence was positive in the cluster of the parafollicular cells also shown to be argyrophilic, the cells proposed to have a monoamine-handling capacity specific for serotonin. These results indicate that indoleamine 2,3-dioxygenase is present in those cells rich in serotonin or active in serotonin biosynthesis and further support our previous contention that the enzyme may play an important role in the regulation of the metabolism of indoleamines and their precursors in such cells.
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Sono M, Taniguchi T, Watanabe Y, Hayaishi O. Indoleamine 2,3-dioxygenase. Equilibrium studies of the tryptophan binding to the ferric, ferrous, and CO-bound enzymes. J Biol Chem 1980; 255:1339-45. [PMID: 7354029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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Taniguchi T, Sono M, Hirata F, Hayaishi O, Tamura M, Hayashi K, Iizuka T, Ishimura Y. Indoleamine 2,3-dioxygenase. Kinetic studies on the binding of superoxide anion and molecular oxygen to enzyme. J Biol Chem 1979; 254:3288-94. [PMID: 218967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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Taniguchi T, Sono M, Hirata F, Hayaishi O, Tamura M, Hayashi K, Iizuka T, Ishimura Y. Indoleamine 2,3-dioxygenase. Kinetic studies on the binding of superoxide anion and molecular oxygen to enzyme. J Biol Chem 1979. [DOI: 10.1016/s0021-9258(18)50757-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Sono M, McCray JA, Asakura T. Effects of chemical modifications of heme on kinetics of carbon monoxide binding to free heme. J Biol Chem 1977; 252:7475-82. [PMID: 914822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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