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Ahmed Laskar A, Younus H. Aldehyde toxicity and metabolism: the role of aldehyde dehydrogenases in detoxification, drug resistance and carcinogenesis. Drug Metab Rev 2019; 51:42-64. [DOI: 10.1080/03602532.2018.1555587] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Amaj Ahmed Laskar
- Enzymology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Hina Younus
- Enzymology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
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2
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NADP-Dependent Aldehyde Dehydrogenase from Archaeon Pyrobaculum sp.1860: Structural and Functional Features. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2016; 2016:9127857. [PMID: 27956891 PMCID: PMC5121451 DOI: 10.1155/2016/9127857] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 08/26/2016] [Accepted: 09/14/2016] [Indexed: 11/17/2022]
Abstract
We present the functional and structural characterization of the first archaeal thermostable NADP-dependent aldehyde dehydrogenase AlDHPyr1147. In vitro, AlDHPyr1147 catalyzes the irreversible oxidation of short aliphatic aldehydes at 60-85°С, and the affinity of AlDHPyr1147 to the NADP+ at 60°С is comparable to that for mesophilic analogues at 25°С. We determined the structures of the apo form of AlDHPyr1147 (3.04 Å resolution), three binary complexes with the coenzyme (1.90, 2.06, and 2.19 Å), and the ternary complex with the coenzyme and isobutyraldehyde as a substrate (2.66 Å). The nicotinamide moiety of the coenzyme is disordered in two binary complexes, while it is ordered in the ternary complex, as well as in the binary complex obtained after additional soaking with the substrate. AlDHPyr1147 structures demonstrate the strengthening of the dimeric contact (as compared with the analogues) and the concerted conformational flexibility of catalytic Cys287 and Glu253, as well as Leu254 and the nicotinamide moiety of the coenzyme. A comparison of the active sites of AlDHPyr1147 and dehydrogenases characterized earlier suggests that proton relay systems, which were previously proposed for dehydrogenases of this family, are blocked in AlDHPyr1147, and the proton release in the latter can occur through the substrate channel.
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3
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The mechanism of discrimination between oxidized and reduced coenzyme in the aldehyde dehydrogenase domain of Aldh1l1. Chem Biol Interact 2013; 202:62-9. [PMID: 23295222 DOI: 10.1016/j.cbi.2012.12.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 12/11/2012] [Accepted: 12/15/2012] [Indexed: 11/20/2022]
Abstract
Aldh1l1, also known as 10-formyltetrahydrofolate dehydrogenase (FDH), contains the carboxy-terminal domain (Ct-FDH), which is a structural and functional homolog of aldehyde dehydrogenases (ALDHs). This domain is capable of catalyzing the NADP(+)-dependent oxidation of short chain aldehydes to their corresponding acids, and similar to most ALDHs it has two conserved catalytic residues, Cys707 and Glu673. Previously, we demonstrated that in the Ct-FDH mechanism these residues define the conformation of the bound coenzyme and the affinity of its interaction with the protein. Specifically, the replacement of Cys707 with an alanine resulted in the enzyme lacking the ability to differentiate between the oxidized and reduced coenzyme. We suggested that this was due to the loss of a covalent bond between the cysteine and the C4N atom of nicotinamide ring of NADP(+) formed during Ct-FDH catalysis. To obtain further insight into the functional significance of the covalent bond between Cys707 and the coenzyme, and the overall role of the two catalytic residues in the coenzyme binding and positioning, we have now solved crystal structures of Ct-FDH in the complex with thio-NADP(+) and the complexes of the C707S mutant with NADP(+) and NADPH. This study has allowed us to trap the coenzyme in the contracted conformation, which provided a snapshot of the conformational processing of the coenzyme during the transition from oxidized to reduced form. Overall, the results of this study further support the previously proposed mechanism by which Cys707 helps to differentiate between the oxidized and reduced coenzyme during ALDH catalysis.
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Tsybovsky Y, Krupenko SA. Conserved catalytic residues of the ALDH1L1 aldehyde dehydrogenase domain control binding and discharging of the coenzyme. J Biol Chem 2011; 286:23357-67. [PMID: 21540484 DOI: 10.1074/jbc.m111.221069] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The C-terminal domain (C(t)-FDH) of 10-formyltetrahydrofolate dehydrogenase (FDH, ALDH1L1) is an NADP(+)-dependent oxidoreductase and a structural and functional homolog of aldehyde dehydrogenases. Here we report the crystal structures of several C(t)-FDH mutants in which two essential catalytic residues adjacent to the nicotinamide ring of bound NADP(+), Cys-707 and Glu-673, were replaced separately or simultaneously. The replacement of the glutamate with an alanine causes irreversible binding of the coenzyme without any noticeable conformational changes in the vicinity of the nicotinamide ring. Additional replacement of cysteine 707 with an alanine (E673A/C707A double mutant) did not affect this irreversible binding indicating that the lack of the glutamate is solely responsible for the enhanced interaction between the enzyme and the coenzyme. The substitution of the cysteine with an alanine did not affect binding of NADP(+) but resulted in the enzyme lacking the ability to differentiate between the oxidized and reduced coenzyme: unlike the wild-type C(t)-FDH/NADPH complex, in the C707A mutant the position of NADPH is identical to the position of NADP(+) with the nicotinamide ring well ordered within the catalytic center. Thus, whereas the glutamate restricts the affinity for the coenzyme, the cysteine is the sensor of the coenzyme redox state. These conclusions were confirmed by coenzyme binding experiments. Our study further suggests that the binding of the coenzyme is additionally controlled by a long-range communication between the catalytic center and the coenzyme-binding domain and points toward an α-helix involved in the adenine moiety binding as a participant of this communication.
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Affiliation(s)
- Yaroslav Tsybovsky
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, USA
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de Carvalho LPS, Ling Y, Shen C, Warren JD, Rhee KY. On the chemical mechanism of succinic semialdehyde dehydrogenase (GabD1) from Mycobacterium tuberculosis. Arch Biochem Biophys 2011; 509:90-9. [PMID: 21303655 DOI: 10.1016/j.abb.2011.01.023] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 01/30/2011] [Accepted: 01/31/2011] [Indexed: 02/06/2023]
Abstract
Succinic semialdehyde dehydrogenases (SSADHs) are ubiquitous enzymes that catalyze the NAD(P)+-coupled oxidation of succinic semialdehyde (SSA) to succinate, the last step of the γ-aminobutyrate shunt. Mycobacterium tuberculosis encodes two paralogous SSADHs (gabD1 and gabD2). Here, we describe the first mechanistic characterization of GabD1, using steady-state kinetics, pH-rate profiles, ¹H NMR, and kinetic isotope effects. Our results confirmed SSA and NADP+ as substrates and demonstrated that a divalent metal, such as Mg²+, linearizes the time course. pH-rate studies failed to identify any ionizable groups with pK(a) between 5.5 and 10 involved in substrate binding or rate-limiting chemistry. Primary deuterium, solvent and multiple kinetic isotope effects revealed that nucleophilic addition to SSA is very fast, followed by a modestly rate-limiting hydride transfer and fast thioester hydrolysis. Proton inventory studies revealed that a single proton is associated with the solvent-sensitive rate-limiting step. Together, these results suggest that product dissociation and/or conformational changes linked to it are rate-limiting. Using structural information for the human homolog enzyme and ¹H NMR, we further established that nucleophilic attack takes place at the Si face of SSA, generating a thiohemiacetal with S stereochemistry. Deuteride transfer to the Pro-R position in NADP+ generates the thioester intermediate and [4A-²H, 4B-¹H] NADPH. A chemical mechanism based on these data and the structural information available is proposed.
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Affiliation(s)
- Luiz Pedro S de Carvalho
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Ave. New York, NY 10065, USA.
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Rodríguez-Zavala JS, Allali-Hassani A, Weiner H. Characterization of E. coli tetrameric aldehyde dehydrogenases with atypical properties compared to other aldehyde dehydrogenases. Protein Sci 2006; 15:1387-96. [PMID: 16731973 PMCID: PMC2242541 DOI: 10.1110/ps.052039606] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Aldehyde dehydrogenases are general detoxifying enzymes, but there are also isoenzymes that are involved in specific metabolic pathways in different organisms. Two of these enzymes are Escherichia coli lactaldehyde (ALD) and phenylacetaldehyde dehydrogenases (PAD), which participate in the metabolism of fucose and phenylalanine, respectively. These isozymes share some properties with the better characterized mammalian enzymes but have kinetic properties that are unique. It was possible to thread the sequences into the known ones for the mammalian isozymes to better understand some structural differences. Both isozymes were homotetramers, but PAD used both NAD+ and NADP+ but with a clear preference for NAD, while ALD used only NAD+. The rate-limiting step for PAD was hydride transfer as indicated by the primary isotopic effect and the absence of a pre-steady-state burst, something not previously found for tetrameric enzymes from other organisms where the rate-limiting step is related to both deacylation and coenzyme dissociation. In contrast, ALD had a pre-steady-state burst indicating that the rate-limiting step was located after the NADH formation, but the rate-limiting step was a combination of deacylation and coenzyme dissociation. Both enzymes possessed esterase activity that was stimulated by NADH; NAD+ stimulated the esterase activity of PAD but not of ALD. Finding enzymes that structurally are similar to the well-characterized mammalian enzymes but have a different rate-limiting step might serve as models to allow us to determine what regulates the rate-limiting step.
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Rodríguez-Zavala JS, Ortiz-Cruz MA, Moreno-Sanchez R. Characterization of an Aldehyde Dehydrogenase from Euglena gracilis. J Eukaryot Microbiol 2006; 53:36-42. [PMID: 16441583 DOI: 10.1111/j.1550-7408.2005.00070.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The free-living protist Euglena gracilis showed an enhanced growth when cultured in the dark with high concentrations of ethanol as carbon source. In a medium containing glutamate/malate plus 1% ethanol, E. gracilis reached a density of 3 x 10(7) cells/ml after 100 h of culture, which was 5 times higher than that attained with glutamate/malate or ethanol separately. This observation suggested the involvement of a highly active aldehyde dehydrogenase in the metabolism of ethanol. Purification of the E. gracilis aldehyde dehydrogenase from the mitochondrial fraction by affinity chromatography yielded an enrichment of 34 times and recovery of 33% of the total mitochondrial activity. SDS-PAGE and molecular exclusion chromatography revealed a native tetrameric protein of 160 kDa. Kinetic analysis showed Km values of 5 and 50 microM for propionaldehyde and NAD(+), respectively, and a Vm value of 1,300 nmol (min x mg protein)(-1). NAD(+) and NADH stimulated the esterase activity of the purified aldehyde dehydrogenase. The present data indicated that the E. gracilis aldehyde dehydrogenase has kinetic and structural properties similar to those of human aldehyde dehydrogenases class 1 and 2.
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Affiliation(s)
- Jose S Rodríguez-Zavala
- Departamento de Bioquímica. Instituto Nacional de Cardiología, Juan Badiano No. 1, Col. Sección XVI, Tlalpan, México D.F. 14080, México.
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8
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Larson HN, Weiner H, Hurley TD. Disruption of the coenzyme binding site and dimer interface revealed in the crystal structure of mitochondrial aldehyde dehydrogenase "Asian" variant. J Biol Chem 2005; 280:30550-6. [PMID: 15983043 PMCID: PMC1262676 DOI: 10.1074/jbc.m502345200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial aldehyde dehydrogenase (ALDH2) is the major enzyme that oxidizes ethanol-derived acetaldehyde. A nearly inactive form of the enzyme, ALDH2*2, is found in about 40% of the East Asian population. This variant enzyme is defined by a glutamate to lysine substitution at residue 487 located within the oligomerization domain. ALDH2*2 has an increased Km for its coenzyme, NAD+, and a decreased kcat, which lead to low activity in vivo. Here we report the 2.1 A crystal structure of ALDH2*2. The structure shows a large disordered region located at the dimer interface that includes much of the coenzyme binding cleft and a loop of residues that form the base of the active site. As a consequence of these structural changes, the variant enzyme exhibits rigid body rotations of its catalytic and coenzyme-binding domains relative to the oligomerization domain. These structural perturbations are the direct result of the inability of lysine 487 to form important stabilizing hydrogen bonds with arginines 264 and 475. Thus, the elevated Km for coenzyme exhibited by this variant probably reflects the energetic penalty for reestablishing this site for productive coenzyme binding, whereas the structural alterations near the active site are consistent with the lowered Vmax.
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Affiliation(s)
- Heather N. Larson
- From the Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202 and the
| | - Henry Weiner
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907
| | - Thomas D. Hurley
- From the Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202 and the
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9
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Weiner H, Wei B, Zhou J. Subunit communication in tetrameric class 2 human liver aldehyde dehydrogenase as the basis for half-of-the-site reactivity and the dominance of the oriental subunit in a heterotetramer. Chem Biol Interact 2001; 130-132:47-56. [PMID: 11306030 DOI: 10.1016/s0009-2797(00)00221-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Data has been published showing that in heterotetrameric liver mitochondrial aldehyde dehydrogenase composed of the active (E487) and the inactive Oriental-variant (K487) subunit, the Oriental variant was dominant and caused the inactivation of the E487 subunit. The published structures of the enzyme showed that the glutamate at position 487 is salt bonded to an arginine (475) in a different subunit. Arg475 was mutated to a glutamine to test for its importance in causing the Oriental variant to be an enzyme with a high Km for NAD and a low specific activity. Unexpectedly, the R475Q mutant exhibited positive cooperativity in NAD binding with a Hill coefficient of 2. Individual heterotetramers composed of subunits of E487 and K487 were produced by making changes to two residues on the surface of the enzyme and then co-expressing both cDNAs in E. coli. The E(3)K form had essentially 50% the activity of the E(4) homotetrameric form while EK(3) had essentially the same properties as did the homotetrameric K(4) Oriental variant. This showed that in a dimer pair composed of one K- and one E- subunit the K-subunit became dominant and caused the inactivation of its E-partner. Further, pre-steady state burst data and steady state kinetic data make it appear that there was one functioning active subunit in each of the dimer pairs that made up the tetrameric enzyme. Thus, the half-of-the-site reactivity is a result of having one functioning and one non-functioning subunit in each dimer pair. The actual structural basis for this is still not understood, but could be related to the E487-R475 inter-dimer salt bond.
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Affiliation(s)
- H Weiner
- Department of Biochemistry, Purdue University, 1153 Biochemistry Building, Purdue University, West Lafayette, 47907-1153, Indiana, USA.
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Shen ML, Benson LM, Johnson KL, Lipsky JJ, Naylor S. Effect of enzyme inhibitors on protein quaternary structure determined by on-line size exclusion chromatography-microelectrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2001; 12:97-104. [PMID: 11142365 DOI: 10.1016/s1044-0305(00)00190-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Aldehyde dehydrogenases (ALDH) are a family of enzymes primarily involved in the oxidation of various aldehydes. Most ALDH enzymes derived from mammalian sources have been shown to exist as homotetramers, consisting of four identical subunits of approximately 54 kDa. The presence of the homotetramer appears to be necessary for enzyme activity. In this study, recombinant rat liver mitochondrial ALDH (rmALDH) was inhibited in vitro with four different inhibitors, namely, disulfiram (MW, 296.5), prunetin (MW, 284.3), benomyl (MW, 290.3), and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) (MW, 351.8). Subsequently, inhibited rmALDH was analyzed by a novel approach of on-line size exclusion chromatography-microelectrospray ionization-mass spectrometry (SEC-muESI-MS) to examine the noncovalent quaternary structural stability of the inhibited enzyme. Analysis of native rmALDH by SEC-muESI-MS revealed predominantly the homotetramer (Mr = approximately 217,457 Da, +/- 0.01%) with some in-source, skimmer-induced dissociation to afford monomer (Mr = approximately 54,360 Da, +/- 0.01%). Both disulfiram and prunetin inhibited rmALDH by >70% and >90%, respectively, but did not disrupt the quaternary structure of rmALDH. Furthermore, there was no detectable change within experimental error (+/- 0.01%) of the disulfiram or the prunetin homotetramers (Mr = approximately 217,448 Da and Mr = approximately 217,446 Da). This may possibly indicate that inhibition occurred via formation of intramolecular disulfide bond at the enzyme active site, or weak affinity noncovalent binding. In contrast, benomyl-inhibited rmALDH homotetramer (>90% inhibition) exhibited a Mr = approximately 217,650 Da (+/- 0.01%) corresponding to two butylcarbamoyl adducts on two of the four enzyme subunits. The skimmer-induced monomer afforded a mixture of unmodified rmALDH (Mr = approximately 54,365 Da, +/- 0.01%) and butylcarbamoylated enzyme (Mr = approximately 54,459 Da, +/- 0.01%). Finally, TPCK (>90% inhibition) modified all four subunits of rmALDH to give Mr = approximately 218,646 Da (+/- 0.01%). In all four cases while significant enzyme inhibition occurred, no destabilization of the quaternary complex was detected.
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Affiliation(s)
- M L Shen
- Mayo Clinic/Foundation, Rochester, Minnesota 55905, USA
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Wang X, Mann CJ, Bai Y, Ni L, Weiner H. Molecular cloning, characterization, and potential roles of cytosolic and mitochondrial aldehyde dehydrogenases in ethanol metabolism in Saccharomyces cerevisiae. J Bacteriol 1998; 180:822-30. [PMID: 9473035 PMCID: PMC106960 DOI: 10.1128/jb.180.4.822-830.1998] [Citation(s) in RCA: 99] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/1997] [Accepted: 12/03/1997] [Indexed: 02/06/2023] Open
Abstract
The full-length DNAs for two Saccharomyces cerevisiae aldehyde dehydrogenase (ALDH) genes were cloned and expressed in Escherichia coli. A 2,744-bp DNA fragment contained an open reading frame encoding cytosolic ALDH1, with 500 amino acids, which was located on chromosome XVI. A 2,661-bp DNA fragment contained an open reading frame encoding mitochondrial ALDH5, with 519 amino acids, of which the N-terminal 23 amino acids were identified as the putative leader sequence. The ALDH5 gene was located on chromosome V. The commercial ALDH (designated ALDH2) was partially sequenced and appears to be a mitochondrial enzyme encoded by a gene located on chromosome XV. The recombinant ALDH1 enzyme was found to be essentially NADP dependent, while the ALDH5 enzyme could utilize either NADP or NAD as a cofactor. The activity of ALDH1 was stimulated two- to fourfold by divalent cations but was unaffected by K+ ions. In contrast, the activity of ALDH5 increased in the presence of K+ ions: 15-fold with NADP and 40-fold with NAD, respectively. Activity staining of isoelectric focusing gels showed that cytosolic ALDH1 contributed 30 to 70% of the overall activity, depending on the cofactor used, while mitochondrial ALDH2 contributed the rest. Neither ALDH5 nor the other ALDH-like proteins identified from the genomic sequence contributed to the in vitro oxidation of acetaldehyde. To evaluate the physiological roles of these three ALDH isoenzymes, the genes encoding cytosolic ALDH1 and mitochondrial ALDH2 and ALDH5 were disrupted in the genome of strain TWY397 separately or simultaneously. The growth of single-disruption delta ald1 and delta ald2 strains on ethanol was marginally slower than that of the parent strain. The delta ald1 delta ald2 double-disruption strain failed to grow on glucose alone, but growth was restored by the addition of acetate, indicating that both ALDHs might catalyze the oxidation of acetaldehyde produced during fermentation. The double-disruption strain grew very slowly on ethanol. The role of mitochondrial ALDH5 in acetaldehyde metabolism has not been defined but appears to be unimportant.
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Affiliation(s)
- X Wang
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA
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Sheikh S, Ni L, Hurley TD, Weiner H. The potential roles of the conserved amino acids in human liver mitochondrial aldehyde dehydrogenase. J Biol Chem 1997; 272:18817-22. [PMID: 9228056 DOI: 10.1074/jbc.272.30.18817] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The sequence alignment of all known aldehyde dehydrogenases showed that only 23 residues were completely conserved (Hempel, J., Nicholas, H., and Lindahl, R. (1993) Protein Sci. 2, 1890-1900). Of these 14 were glycines and prolines. Site-directed mutagenesis showed that Cys302 was the essential nucleophile and that Glu268 was the general base necessary to activate Cys302 for both the dehydrogenase and esterase reaction. Here we report the mutational analysis of other conserved residues possessing reactive side chains Arg84, Lys192, Thr384, Glu399, and Ser471, along with partially conserved Glu398 and Lys489, to determine their involvement in the catalytic process and correlate these finding with the known structure of mitochondrial ALDH (Steinmetz, C. G., Xie, P.-G., Weiner, H., and Hurley, T. D. (1997) Structure 5, 701-711). No residue was found to be absolutely essential, but all the mutations caused a decrease in the specific activity of the enzyme. None of the mutations affected the Km for aldehyde significantly, although k3, the rate constant calculated for aldehyde binding was decreased. The Km and dissociation constant (Kia) for NAD+ increased significantly for K192Q and S471A compared with the native enzyme. Mutations of only Lys192 and Glu399, both NAD+-ribose binding residues, led to a change in the rate-limiting step such that hydride transfer became rate-limiting, not deacylation. Esterase activity of all mutants decreased even though mutations affected different catalytic steps in the dehydrogenase reaction.
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Affiliation(s)
- S Sheikh
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA
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Steinmetz CG, Xie P, Weiner H, Hurley TD. Structure of mitochondrial aldehyde dehydrogenase: the genetic component of ethanol aversion. Structure 1997; 5:701-11. [PMID: 9195888 DOI: 10.1016/s0969-2126(97)00224-4] [Citation(s) in RCA: 259] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND The single genetic factor most strongly correlated with reduced alcohol consumption and incidence of alcoholism is a naturally occurring variant of mitochondrial aldehyde dehydrogenase (ALDH2). This variant contains a glutamate to lysine substitution at position 487 (E487K). The E487K variant of ALDH2 is found in approximately 50% of the Asian population, and is associated with a phenotypic loss of ALDH2 activity in both heterozygotes and homozygotes. ALDH2-deficient individuals exhibit an averse response to ethanol consumption, which is probably caused by elevated levels of blood acetaldehyde. The structure of ALDH2 is important for the elucidation of its catalytic mechanism, to gain a clear understanding of the contribution of ALDH2 to the genetic component of alcoholism and for the development of specific ALDH2 inhibitors as potential drugs for use in the treatment of alcoholism. RESULTS The X-ray structure of bovine ALDH2 has been solved to 2.65 A in its free form and to 2.75 A in a complex with NAD+. The enzyme structure contains three domains; two dinucleotide-binding domains and a small three-stranded beta-sheet domain, which is involved in subunit interactions in this tetrameric enzyme. The E487K mutation occurs in this small oligomerization domain and is located at a key interface between subunits immediately below the active site of another monomer. The active site of ALDH2 is divided into two halves by the nicotinamide ring of NAD+. Adjacent to the A-side (Pro-R) of the nicotinamide ring is a cluster of three cysteines (Cys301, Cys302 and Cys303) and adjacent to the B-side (Pro-S) are Thr244, Glu268, Glu476 and an ordered water molecule bound to Thr244 and Glu476. CONCLUSIONS Although there is a recognizable Rossmann-type fold, the coenzyme-binding region of ALDH2 binds NAD+ in a manner not seen in other NAD+-binding enzymes. The positions of the residues near the nicotinamide ring of NAD+ suggest a chemical mechanism whereby Glu268 functions as a general base through a bound water molecule. The sidechain amide nitrogen of Asn169 and the peptide nitrogen of Cys302 are in position to stabilize the oxyanion present in the tetrahedral transition state prior to hydride transfer. The functional importance of residue Glu487 now appears to be due to indirect interactions of this residue with the substrate-binding site via Arg264 and Arg475.
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Affiliation(s)
- C G Steinmetz
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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Zhou J, Weiner H. Binding of thyroxine analogs to human liver aldehyde dehydrogenases. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 245:123-8. [PMID: 9128732 DOI: 10.1111/j.1432-1033.1997.00123.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A fragment of a cytosolic thyroid-hormone-binding protein from Xenopus liver was reported to be 92-100% identical to residues 236-258 in several cytosolic aldehyde dehydrogenases [Yamauchi, K. & Tata, J. R. (1994) Eur. J. Biochem. 225, 1105-1112], which have been proposed to form part of the hinge region necessary to bind the adenosine moiety of NAD. Here we investigated the effects of two thyroxine analogs, 3,3',5-triiodo-L-thyronine and 3,3',5-triiodothyroacetic acid, on purified human liver mitochondrial and cytosolic aldehyde dehydrogenases. The compounds were found to be competitive inhibitors against NAD and uncompetitive inhibitors with respect to aldehyde. At pH 7.4, the apparent Ki values were in the micromolar range when the concentration of NAD was varied. The inhibition against recombinantly expressed mutant forms of aldehyde dehydrogenase, which possessed diminished NAD binding, was determined. Essentially no differences were found between the native enzyme and the mutants, showing that the analog binding was not affected by altering the NAD-binding site. Furthermore, the analogs could displace NAD but not NADH from the enzyme. These findings indicated that the binding of NAD differed from that of NADH, and that aldehyde dehydrogenases, like other dehydrogenases, can be inhibited by thyroxine analogs.
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Affiliation(s)
- J Zhou
- Department of Biochemistry, Purdue University, West Lafayette, USA
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15
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Sheikh S, Weiner H. Allosteric inhibition of human liver aldehyde dehydrogenase by the isoflavone prunetin. Biochem Pharmacol 1997; 53:471-8. [PMID: 9105397 DOI: 10.1016/s0006-2952(96)00837-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Isoflavonoid derivatives including prunetin (4',5-dihydroxy-7-methoxyisoflavone) were shown to be potent inhibitors of human aldehyde dehydrogenases (Keung W-M and Vallee BL, Proc Natl Acad Sci USA 90: 1247-1251, 1993). The inhibition reaction was reinvestigated using recombinantly expressed human aldehyde dehydrogenases. The kinetic analyses showed that prunetin inhibits competitively against both NAD and propionaldehyde with the mitochondrial and cytoplasmic enzymes. The Ki value for the mitochondrial enzyme was much lower than for the cytoplasmicenzyme. A mixed pattern of inhibition was obtaiend with the mitochondrial enzyme in the presence of Mg2+. Only one mole of prunetin binds per mole of tetrameric mitochondrial enzyme, which remains unaltered in the presence of Mg2+. Prunetin did not displace NADH from the enzyme-NADH complex. Propionaldehyde did not reverse the loss of fluorescence obtained due to enzyme-prunetin complex formation, indicating that prunetin may not be interacting at the substrate site. The esterase activity of the mitochondrial enzyme was also inhibited by prunetin in a competitive manner. The replacement of lysine 192 by glutamine resulted in a mutant with a 20% kcat and a 100-fold increase in the Km for NAI) compared with the native enzyme. However, the Ki value of prunetin against NAD was similar to that observed with the native enzyme. Prunetin, even at a very high concentration, was not an inhibitor of alcohol and malate dehydrogenase. It was concluded that prunetin may act as an allosteric inhibitor of aldehyde dehydrogenase.
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Affiliation(s)
- S Sheikh
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907-1153, USA
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Sheikh S, Ni L, Weiner H. Mutation of the conserved amino acids of mitochondria aldehyde dehydrogenase. Role of the conserved residues in the mechanism of reaction. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1997; 414:195-200. [PMID: 9059621 DOI: 10.1007/978-1-4615-5871-2_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- S Sheikh
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA
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Weiner H, Sheikh S, Zhou J, Wang X. Subunit interactions in mammalian liver aldehyde dehydrogenases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1997; 414:181-5. [PMID: 9059619 DOI: 10.1007/978-1-4615-5871-2_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- H Weiner
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA
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Wang X, Sheikh S, Saigal D, Robinson L, Weiner H. Heterotetramers of human liver mitochondrial (class 2) aldehyde dehydrogenase expressed in Escherichia coli. A model to study the heterotetramers expected to be found in Oriental people. J Biol Chem 1996; 271:31172-8. [PMID: 8940116 DOI: 10.1074/jbc.271.49.31172] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
About 50% of the Oriental population have less liver mitochondrial aldehyde dehydrogenase (ALDH2) activity than do other people. It was found that they possessed an enzyme with a lysine at position 487 (E487K) instead of glutamate (Glu487). We previously found that the Km for NAD of recombinant human and rat E487K enzymes increased more than 150-fold (Farrés, J., Wang X., Takahashi, K., Cunningham, S. J. , Wang, T.T., and Weiner, H (1994) J. Biol. Chem. 269, 13854-13860). Many aldehyde dehydrogenase-deficient people were found to be heterozygous when genotyped for ALDH2. In this study liver tissue from heterozygous people was analyzed and found to possess mRNAs for both the glutamate and the lysine subunits. Western blot analysis showed that the glutamate subunit was present. The cDNAs for Glu487 and E487K were coexpressed on one plasmid in Escherichia coli, and the enzyme forms were separated from each other by isoelectric focusing to show that heterotetramers were formed. Only one Km value for NAD could be measured with the purified heterotetrameric enzyme that possessed just 16-18% activity of the glutamate homotetrameric enzyme. The E487K homotetramers had 8% specific activity of the Glu487 enzyme. There was no pre-steady state burst of NADH formation with the heterotetramer, a property found with the glutamate enzyme. Similar results were found for the coexpressed rat liver enzyme, except that a higher specific activity, 48%, was obtained. Thus, we conclude that presence of the lysine subunit altered the activity of the glutamate subunit in the heterotetramer to make it function more like an E487K enzyme.
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Affiliation(s)
- X Wang
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153, USA.
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19
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Effects of changing glutamate 487 to lysine in rat and human liver mitochondrial aldehyde dehydrogenase. A model to study human (Oriental type) class 2 aldehyde dehydrogenase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36725-x] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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20
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Ghenbot G, Weiner H. Purification of liver aldehyde dehydrogenase by p-hydroxyacetophenone-sepharose affinity matrix and the coelution of chloramphenicol acetyl transferase from the same matrix with recombinantly expressed aldehyde dehydrogenase. Protein Expr Purif 1992; 3:470-8. [PMID: 1486275 DOI: 10.1016/1046-5928(92)90064-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
p-Hydroxyacetophenone was coupled to epoxy-activated Sepharose 6B to generate an affinity chromatographic matrix to purify aldehyde dehydrogenase. Purified beef liver mitochondrial aldehyde dehydrogenase specifically bound to the support and could be eluted with p-hydroxyacetophenone. A post-ammonium sulfate (30-55%) fraction of bovine liver was applied to the affinity gel column and aldehyde dehydrogenase was effectively purified, although not to complete homogeneity, indicating the potential selectivity of the matrix. Both beef liver cytosolic and mitochondrial aldehyde dehydrogenase bound to the column. A post-Cibacron blue Sepharose Cl-6B affinity-fractionated liver mitochondrial aldehyde dehydrogenase was purified to complete homogeneity by p-hydroxyacetophenone-Sepharose, thus eliminating the need for the isoelectric focusing step often employed. p-Hydroxyacetophenone was found to be a competitive inhibitor against propionaldehyde and noncompetitive against NAD. Escherichia coli lysates of recombinantly expressed aldehyde dehydrogenase were purified from E. coli lysates with one major 25-kDa protein contaminant also binding to the column, as detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The 25-kDa contaminant was found to be chloramphenicol acetyl transferase from sequence analysis and binding studies.
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Affiliation(s)
- G Ghenbot
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907-1153
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22
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Rawles JW, Rhodes DL, Potter JJ, Mezey E. Characterization of human erythrocyte aldehyde dehydrogenase. Biochem Pharmacol 1987; 36:3715-22. [PMID: 3675626 DOI: 10.1016/0006-2952(87)90025-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Human erythrocyte aldehyde dehydrogenase was purified to homogeneity. The enzyme exhibited a single band of activity on starch gel electrophoresis and on isoelectric focusing. It was a tetramer with an estimated molecular weight of 230,000 daltons and an isoelectric point of 5.0. Its pH optimum of 8.5, Michaelis-Menten constant for acetaldehyde of 46 microM, and high sensitivity to noncompetitive inhibition by disulfiram resembled human liver cytosolic aldehyde dehydrogenase. Low concentrations of magnesium (5-10 microM) resulted in enhancement of erythrocyte aldehyde dehydrogenase activity, whereas higher physiological concentrations of magnesium resulted in uncompetitive inhibition of enzyme activity. Magnesium inhibited the enzyme activity by increasing the binding of NADH to the enzyme as had been found to be the case for the inhibitory effect of magnesium on the human liver cytosolic enzyme. Erythrocyte aldehyde dehydrogenase may metabolize small amounts of acetaldehyde escaping the liver during ethanol metabolism and protect extrahepatic tissues from acetaldehyde toxicity.
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Affiliation(s)
- J W Rawles
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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23
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Mejia NR, Rios-Orlandi EM, MacKenzie RE. NAD-dependent methylenetetrahydrofolate dehydrogenase-methenyltetrahydrofolate cyclohydrolase from ascites tumor cells. Purification and properties. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67686-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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24
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Dickinson FM, Haywood GW. The effects of Mg2+ on certain steps in the mechanisms of the dehydrogenase and esterase reactions catalysed by sheep liver aldehyde dehydrogenase. Support for the view that dehydrogenase and esterase activities occur at the same site on the enzyme. Biochem J 1986; 233:877-83. [PMID: 3707531 PMCID: PMC1153111 DOI: 10.1042/bj2330877] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Stopped-flow experiments in spectrophotometric and fluorescence modes reveal different aspects of the aldehyde dehydrogenase mechanism. Spectrophotometric experiments show a rapid burst of NADH production whose course is not affected by Mg2+. The slower burst seen in the fluorescence mode is markedly accelerated by Mg2+. It is argued that the fluorescence burst accompanies acyl-enzyme hydrolysis and, therefore, that Mg2+ increases the rate of this process. Experiments on the hydrolysis of p-nitrophenyl propionate indicate that acyl-enzyme hydrolysis is indeed accelerated by Mg2+ and a combination of Mg2+ and NADH. Vmax. values for p-nitrophenyl propionate hydrolysis in the presence of NADH and NADH and Mg2+ agree closely with the specific rates of acyl hydrolysis from the E . NADH . acyl and E . NADH . acyl . Mg2+ complexes seen in the dehydrogenase reaction with propionaldehyde. These observations support the view that esterase and dehydrogenase activities occur at the same site on the enzyme. Other evidence is presented to support this conclusion.
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25
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Allanson S, Dickinson FM. The removal of cytosolic-type aldehyde dehydrogenase from preparations of sheep liver mitochondrial aldehyde dehydrogenase and the unusual properties of the purified mitochondrial enzyme in assays. Biochem J 1984; 224:163-9. [PMID: 6439192 PMCID: PMC1144409 DOI: 10.1042/bj2240163] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The pI approximately 5.2 isoenzymes of mitochondrial aldehyde dehydrogenase were separated from the other isoenzymes by pH-gradient chromatography on DEAE-Sephacel. The pI approximately 5.2 material is immunologically identical with cytosolic aldehyde dehydrogenase. It also shows sensitivity to 20 microM-disulfiram and insensitivity to 4M-urea in assays. These and other criteria seem to establish that the material is identical with the cytosolic enzyme. Mitochondrial enzyme that had been purified to remove pI approximately 5.2 isoenzymes shows concentration-dependent lag phases in assays. These effects are possibly due to the slow establishment of equilibrium between tetramer and either dimers or monomers, with the dissociated species being intrinsically more active than the tetramer.
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26
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Vallari RC, Pietruszko R. Interaction of Mg2+ with human liver aldehyde dehydrogenase. I. Species difference in the mitochondrial isozyme. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)42934-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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27
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Vallari RC, Pietruszko R. Interaction of Mg2+ with human liver aldehyde dehydrogenase. II. Mechanism and site of interaction. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)42935-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Leonard NJ. Etheno-substituted nucleotides and coenzymes: fluorescence and biological activity. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1984; 15:125-99. [PMID: 6365449 DOI: 10.3109/10409238409102299] [Citation(s) in RCA: 130] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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29
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Hart GJ, Dickinson FM. The coenzyme-binding characteristics of highly purified preparations of sheep liver cytoplasmic aldehyde dehydrogenase. Biochem J 1983; 211:363-71. [PMID: 6409094 PMCID: PMC1154368 DOI: 10.1042/bj2110363] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The binding of NADH and NAD+ by cytoplasmic aldehyde dehydrogenase was studied by various direct and indirect methods. At pH 7.0 at 25 degrees C there appears to be approx. 1 binding site for both nucleotides per 200 000 daltons of protein, although the NAD+-binding results are rather uncertain. Estimates of the dissociation constants of the E . NADH and E . NAD+ complexes under the stated conditions are also presented. Preparations of enzyme are sometimes found to contain significant amounts of very tightly bound NAD+ and NADH. The implications of these findings are discussed.
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30
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Bennett AF, Buckley PD, Blackwell LF. Inhibition of the dehydrogenase activity of sheep liver cytoplasmic aldehyde dehydrogenase by magnesium ions. Biochemistry 1983; 22:776-84. [PMID: 6838823 DOI: 10.1021/bi00273a011] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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31
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Weiner H, Takahashi K. Effects of magnesium and calcium on mitochondrial and cytosolic liver aldehyde dehydrogenases. Pharmacol Biochem Behav 1983; 18 Suppl 1:109-12. [PMID: 6634825 DOI: 10.1016/0091-3057(83)90155-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The effects of Mg2+ and Ca2+ ions on the activities of mitochondrial and cytosolic aldehyde dehydrogenases isolated from horse, rat, and beef livers were investigated in 0.1 M sodium phosphate, pH 7.5, at 25 degrees C. As with the Mg2+-enhancement of the horse liver mitochondrial enzyme [17], Mg2+-activation was observed for the mitochondrial enzymes from rat and beef. The cytosolic enzymes from horse, rat, and beef livers were inhibited in the presence of Mg2+ ions. The effects of Ca2+ ions on the activity were essentially the same as those observed in the presence of Mg2+ ions; the mitochondrial isozymes were activated while the cytosolic isozymes were inhibited. The fact that only the activity of mitochondrial forms of mammalian liver aldehyde dehydrogenase was enhanced by Ca2+ or Mg2+ ions may be related to the in vivo regulation of aldehyde metabolism, a presumed mitochondrial event.
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32
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Kitson TM. Further studies of the action of disulfiram and 2,2'-dithiodipyridine on the dehydrogenase and esterase activities of sheep liver cytoplasmic aldehyde dehydrogenase. Biochem J 1982; 203:743-54. [PMID: 7115312 PMCID: PMC1158291 DOI: 10.1042/bj2030743] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
1. Pre-modification of cytoplasmic aldehyde dehydrogenase by disulfiram results in the same extent of inactivation when the enzyme is subsequently assayed as a dehydrogenase or as an esterase. 2. 4-Nitrophenyl acetate protects the enzyme against inactivation by disulfiram, particularly well in the absence of NAD+. Some protection is also provided by chloral hydrate and indol-3-ylacetaldehyde (in the absence of NAD+). 3. When disulfiram is prevented from reacting at its usual site by the presence of 4-nitrophenyl acetate, it reacts elsewhere on the enzyme molecule without causing inactivation. 4. Enzyme in the presence of aldehyde and NAD+ is not at all protected against disulfiram. It is proposed that, under these circumstances, disulfiram reacts with the enzyme-NADH complex formed in the enzyme-catalysed reaction. 5. Modification by disulfiram results in a decrease in the amplitude of the burst of NADH formation during the dehydrogenase reaction, as well as a decrease in the steady-state rate. 6. 2,2'-Dithiodipyridine reacts with the enzyme both in the absence and presence of NAD+. Under the former circumstances the activity of the enzyme is little affected, but when the reaction is conducted in the presence of NAD+ the enzyme is activated by approximately 2-fold and is then relatively insensitive to the inactivatory effect of disulfiram. 7. Enzyme activated by 2,2'-dithiodipyridine loses most of its activity when stored over a period of a few days at 4 degrees C, or within 30 min when treated with sodium diethyldithiocarbamate. 8. Points for and against the proposal that the disulfiram-sensitive groups are catalytically essential are discussed.
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33
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Hempel J, Pietruszko R. Selective chemical modification of human liver aldehyde dehydrogenases E1 and E2 by iodoacetamide. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)68528-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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34
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Takahashi K, Weiner H, Filmer DL. Effects of pH on horse liver aldehyde dehydrogenase: alterations in metal ion activation, number of functioning active sites, and hydrolysis of the acyl intermediate. Biochemistry 1981; 20:6225-30. [PMID: 7306510 DOI: 10.1021/bi00524a049] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The reactivity of the mitochondrial (pI = 5) isoenzyme of horse liver aldehyde dehydrogenase was determined by studying the effects of pH on steady-state velocity, burst magnitude, and molecular weight of the enzyme in the absence and presence of Mg2+ ions. The Mg2+ ion activation of the steady-state velocity at pH 7.5 has been explained through a mechanism involving alteration of the tetrameric enzyme, functioning with half-of-the-sites reactivity, to a dimeric enzyme, functioning with all-of-the-sites reactivity [Takahashi, K., & Weiner, H. (1980) J. Biol. Chem. 255, 8206-8209]. With increasing pH, the tetrameric enzyme dissociated even in the absence of Mg2+ ions to the more active dimeric state. The pH-dependent dissociation was governed by proton release from a group with pK = 9.5. After correcting for the increased number of functioning active sites, determined from the pre-steady-state burst, we calculated that elevated pH also caused an increase in the velocity of the rate-limiting step, hydrolysis of the acyl-enzyme intermediate. This event was governed by the ionization of two groups, with pK = 7.2 and 9.5, respectively. If these groups are directly involved in the catalytic step, a mechanism involving histidine acting as a general base can be proposed for the former group. The latter group may be involved in a charge relay activation process which only occurs at elevated, nonphysiological pH. The importance of the latter is questionable, as there is only a 3-fold increase in Vmax when this group is involved in catalysis.
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