1
|
Tang W, Li H, Doud EH, Chen Y, Choing S, Plaza C, Kelleher NL, Poulos TL, Silverman RB. Mechanism of Inactivation of Neuronal Nitric Oxide Synthase by (S)-2-Amino-5-(2-(methylthio)acetimidamido)pentanoic Acid. J Am Chem Soc 2015; 137:5980-9. [PMID: 25874809 PMCID: PMC4431946 DOI: 10.1021/jacs.5b01202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Nitric oxide synthase (NOS) catalyzes the conversion of l-arginine to l-citrulline and the second messenger nitric oxide. Three mechanistic pathways are proposed for the inactivation of neuronal NOS (nNOS) by (S)-2-amino-5-(2-(methylthio)acetimidamido)pentanoic acid (1): sulfide oxidation, oxidative dethiolation, and oxidative demethylation. Four possible intermediates were synthesized. All compounds were assayed with nNOS, their IC50, KI, and kinact values were obtained, and their crystal structures were determined. The identification and characterization of the products formed during inactivation provide evidence for the details of the inactivation mechanism. On the basis of these studies, the most probable mechanism for the inactivation of nNOS involves oxidative demethylation with the resulting thiol coordinating to the cofactor heme iron. Although nNOS is a heme-containing enzyme, this is the first example of a NOS that catalyzes an S-demethylation reaction; the novel mechanism of inactivation described here could be applied to the design of inactivators of other heme-dependent enzymes.
Collapse
Affiliation(s)
- Wei Tang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Emma H. Doud
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Yunqiu Chen
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Stephanie Choing
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Carla Plaza
- Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Neil L. Kelleher
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Thomas L. Poulos
- Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Richard B. Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| |
Collapse
|
2
|
Affiliation(s)
- Osvaldo Lanzalunga
- a Dipartimento di Chimica, Università di Roma “La Sapienza” and Istituto CNR di Metodologie Chimiche (IMC-CNR) , Sezione Meccanismi di Reazione , P.le Aldo Moro 5, Rome , Italy
| |
Collapse
|
3
|
Scientific Opinion on Flavouring Group Evaluation 08, Revision 5 (FGE.08Rev5): Aliphatic and alicyclic mono‐, di‐, tri‐, and polysulphides with or without additional oxygenated functional groups from chemical groups 20 and 30. EFSA J 2012. [DOI: 10.2903/j.efsa.2012.2837] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
4
|
Scientific Opinion on Flavouring Group Evaluation 08, Revision 4 (FGE.08Rev4): Aliphatic and alicyclic mono-, di-, tri-, and polysulphides with or without additional oxygenated functional groups from chemical groups 20 and 30. EFSA J 2012. [DOI: 10.2903/j.efsa.2012.2455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
5
|
Del Giacco T, Lanzalunga O, Mazzonna M, Mencarelli P. Structural and Solvent Effects on the C–S Bond Cleavage in Aryl Triphenylmethyl Sulfide Radical Cations. J Org Chem 2012; 77:1843-52. [DOI: 10.1021/jo202418d] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Tiziana Del Giacco
- Dipartimento di Chimica and
Centro di Eccellenza Materiali Innovativi Nanostrutturati, Università di Perugia, via Elce di Sotto 8,
06123 Perugia, Italy
| | - Osvaldo Lanzalunga
- Dipartimento di Chimica and
Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione
c/o Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy
| | - Marco Mazzonna
- Dipartimento di Chimica and
Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione
c/o Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy
| | - Paolo Mencarelli
- Dipartimento di Chimica and
Istituto CNR di Metodologie Chimiche-IMC, Sezione Meccanismi di Reazione
c/o Dipartimento di Chimica, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy
| |
Collapse
|
6
|
Scientific Opinion on Flavouring Group Evaluation 8, Revision 3 (FGE.08Rev3): Aliphatic and alicyclic mono-, di-, tri-, and polysulphides with or without additional oxygenated functional groups from chemical groups 20 and 30. EFSA J 2011. [DOI: 10.2903/j.efsa.2011.1988] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
7
|
Flavouring Group Evaluation 08 Rev2 (FGE.08 Rev2): Aliphatic and alicyclic mono-, di-, tri-, and polysulphides with or without additional oxygenated functional groups from chemical groups 20 and 30. EFSA J 2010. [DOI: 10.2903/j.efsa.2010.1408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
8
|
Flavouring Group Evaluation 8, Revision 1 (FGE.08Rev1): Aliphatic and alicyclic mono-, di-, tri-, and polysulphides with or without additional oxygenated functional groups from chemical groups 20 and 30. EFSA J 2010. [DOI: 10.2903/j.efsa.2010.1021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
9
|
Fauve A, Renard MF, Veschambre H, Madesclaire M, Roche D. Microbial Oxidation of Vinyl Sulfides to Chiral sulfoxides. ACTA ACUST UNITED AC 2009. [DOI: 10.3109/10242429109000690] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Annie Fauve
- Laboratoire de Chimie Organique Biologique, URA 485 du CNRS, F-63177, Aubiére Cedex, France
| | - Michel F. Renard
- Groupe de Pharmacochimie, UFR de Pharmacie, BP 38, Clermont-Ferrand, France
| | - Henri Veschambre
- Groupe de Pharmacochimie, UFR de Pharmacie, BP 38, Clermont-Ferrand, France
| | - Michel Madesclaire
- Groupe de Pharmacochimie, UFR de Pharmacie, BP 38, Clermont-Ferrand, France
| | - Danielle Roche
- Groupe de Pharmacochimie, UFR de Pharmacie, BP 38, Clermont-Ferrand, France
| |
Collapse
|
10
|
Application (Reference EFSA‐GMO‐NL‐2008‐51) for the placing on the market of glyphosate tolerant genetically modified cotton GHB614, for food and feed uses, import and processing under Regulation (EC) No 1829/2003 from Bayer CropScience. EFSA J 2009. [DOI: 10.2903/j.efsa.2009.985] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
11
|
Pievo R, Gullotti M, Monzani E, Casella L. Tyrosinase catalyzes asymmetric sulfoxidation. Biochemistry 2008; 47:3493-8. [PMID: 18293936 DOI: 10.1021/bi702421b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mushroom tyrosinase was found to catalyze the oxidation of organic sulfides to sulfoxides in the presence of a catechol as cosubstrate, in a reaction which is unprecedented for this enzyme and resembles those performed by external monooxygenases. Only the oxy form of the enzyme is in fact capable of oxidizing the sulfide in a two-electron process, while the resulting met form can only be recycled by reduction with catechol. The cosubstrate competes with the sulfide also in the reaction with oxy-tyrosinase. For this reason, the sulfoxidation of thioanisole in the presence of l-3,4-dihydroxyphenylalanine (L-dopa) occurs with moderate yields ( approximately 20%) but high enantioselectivity ( approximately 85% e.e.), and favors ( S)-methyl phenyl sulfoxide. The enantioselectivity can be further increased to >90% when excess ascorbic acid is added to the reaction to limit enzyme inactivation by the quinones produced by L-dopa oxidation. An experiment using (18)O 2 showed that 18-O incorporation into methyl phenyl sulfoxide was above 95%, confirming that the mechanism of the sulfoxidation involves oxygen transfer from oxy-tyrosinase to the sulfide.
Collapse
Affiliation(s)
- Roberta Pievo
- Dipartimento di Chimica Inorganica, Metallorganica e Analitica - Università di Milano, Istituto ISTM-CNR 20133 Milano, Italy
| | | | | | | |
Collapse
|
12
|
Testa B, Krämer SD. The biochemistry of drug metabolism--an introduction: Part 2. Redox reactions and their enzymes. Chem Biodivers 2007; 4:257-405. [PMID: 17372942 DOI: 10.1002/cbdv.200790032] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This review continues a general presentation of the metabolism of drugs and other xenobiotics started in a recent issue of Chemistry & Biodiversity. This Part 2 presents the numerous oxidoreductases involved, their nomenclature, relevant biochemical properties, catalytic mechanisms, and the very diverse reactions they catalyze. Many medicinally, environmentally, and toxicologically relevant examples are presented and discussed. Cytochromes P450 occupy a majority of the pages of Part 2, but a large number of relevant oxidoreductases are also considered, e.g., flavin-containing monooxygenases, amine oxidases, molybdenum hydroxylases, peroxidases, and the innumerable dehydrogenases/reductases.
Collapse
Affiliation(s)
- Bernard Testa
- Department of Pharmacy, University Hospital Centre (CHUV), Rue du Bugnon, CH-1011 Lausanne.
| | | |
Collapse
|
13
|
|
14
|
Cashman JR. Stereoselectivity in S- and N-oxygenation by the mammalian flavin-containing and cytochrome P-450 monooxygenases. Drug Metab Rev 1998; 30:675-707. [PMID: 9844806 DOI: 10.3109/03602539808996327] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In general, the use of stereoselectivity studies in examining the contribution of monooxygenases or other catalysts to the N- and S-oxidation of drugs, xenobiotics and endogenous substrates provides a useful method to distinguish enzymatic from nonenzymatic processes. Recent developments in this active area of research have been rapid, presumably due to advances in bioanalytical chemistry, chiral stationary-phase HPLC, and attendant breakthroughs in the instruments to measure centers of chirality. This research area has also been aided by the availability of enzymes and other catalysts. In light of the ever-increasing necessity for new single-isomer drugs, metabolites, and other chiral drug market materials, the demand for stereoselectivity information in the drug development business should continue to expand. In the future, demand for enantiomeric intermediates and metabolites to be studied in their own right for pharmacological activity will undoubtedly increase. Finally, technologies related to the creation or characterization of enantiomerically pure drugs or their metabolites presumably will grow because of the increased number of compounds entering the drug development pipeline due to combinatorial chemistry.
Collapse
Affiliation(s)
- J R Cashman
- Human BioMolecular Research Institute, San Diego, California 92121, USA
| |
Collapse
|
15
|
Oxidations of benzyl and phenethyl phenyl sulfides. Implications for the mechanism of the microsomal and biomimetic oxidation of sulfides. Tetrahedron 1997. [DOI: 10.1016/s0040-4020(97)00560-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
16
|
Baciocchi E, Crescenzi C, Lanzalunga O. Photoinduced electron transfer reactions of benzyl phenyl sulfides promoted by 9,10-dicyanoanthracene. Tetrahedron 1997. [DOI: 10.1016/s0040-4020(97)00119-1] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
17
|
Guengerich FP, Yun CH, Macdonald TL. Evidence for a 1-electron oxidation mechanism in N-dealkylation of N,N-dialkylanilines by cytochrome P450 2B1. Kinetic hydrogen isotope effects, linear free energy relationships, comparisons with horseradish peroxidase, and studies with oxygen surrogates. J Biol Chem 1996; 271:27321-9. [PMID: 8910308 DOI: 10.1074/jbc.271.44.27321] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Many enzymes catalyze N-dealkylations of alkylamines, including cytochrome P450 (P450) and peroxidase enzymes. Peroxidases, exemplified by horseradish peroxidase (HRP), are generally accepted to catalyze N-dealkylations via 1-electron transfer processes. Several lines of evidence also support a 1-electron mechanism for many P450 reactions, although this view has been questioned in light of reported trends for kinetic hydrogen isotope effects for N-demethylation with a series of 4-substituted N,N-dimethylanilines. No continuous trend for an increase of isotope effects with the electronic parameters of para-substitution was seen for the P450 2B1-catalyzed reactions in this study. The larger value seen with the 4-nitro derivative is consistent with a shift in mechanism due to either a reversible electron transfer step preceding deprotonation or to a hydrogen atom abstraction mechanism. With HRP, the trend is to lower isotope effects with para electron-withdrawing substituents, due to an apparent shift in rate-limiting steps. Biomimetic model high-valent porphyrins showed reduction rates with variously 4-substituted N,N-dialkylanilines that were consistent with a positively charged intermediate; such relationships were not seen for anisole O-demethylation with P450 2B1. In contrast to the case with the NADPH-supported P450 reactions, high deuterium isotope effects ( approximately 7) were seen in the N-dealkylations supported by the oxygen surrogate iodosylbenzene. With iodosylbenzene, colored aminium radicals were observed in the oxidations of aminopyrine, N,N-dimethyl-4-aminothioanisole, and 4-methoxy-N,N-dimethylaniline. With the latter compound, a substantial intermolecular deuterium isotope effect was observed for N-demethylation. In the N-dealkylation of N-ethyl,N-methylaniline by P450 2B1 (NADPH-supported), the ratio of N-demethylation to N-deethylation was 16. Although it is probably possible for P450s to catalyze amine N-dealkylations via hydrogen atom abstraction when such a course is electronically or sterically favored, we interpret the evidence to favor a 1-electron pathway with N,N-dialkylamines with P450 2B1 as well as HRP and several biomimetic models.
Collapse
Affiliation(s)
- F P Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | | | | |
Collapse
|
18
|
Abstract
1. Biological and biomimetic oxidations of thioethers are reviewed. 2. gamma-Radiolysis, pulse radiolysis, photochemical, chemical, and electrochemical methods for generating sulphur cation radicals are discussed and exemplified. 3. The major reactions of sulphur cation radicals: nucleophilic attack, electron transfer, decarboxylation, reaction with O2, C-S, C-C, and alpha-C-M bond cleavages, sulphur abstraction, and rearrangements are presented.
Collapse
Affiliation(s)
- R S Glass
- Department of Chemistry, University of Arizona, Tucson 85721, USA
| |
Collapse
|
19
|
Guengerich FP, Okazaki O, Seto Y, Macdonald TL. Radical cation intermediates in N-dealkylation reactions. Xenobiotica 1995; 25:689-709. [PMID: 7483667 DOI: 10.3109/00498259509061886] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
1. A number of mechanistic possibilities exist for P450-catalysed N-dealkylation and have been considered over the years, including C- and N-hydroxylation and sequential electron transfer (SET). With peroxidases the evidence strongly favours SET and free radicals can be detected. Any mechanism must account for lack of incorporation of label from H218O into product by P450s and the high kinetic deuterium isotope effects that are seen in N-dealkylation reactions catalysed by peroxidases but not P450s. 2. Several lines of evidence support a role for SET in P450 amine oxidations, including Hammett analysis, products of dihydropyridine oxidations, and products of mechanism-based inhibition by strained cycloalkylamines. 3. The hypothesis was considered that the P450s act via base catalysis to deprotonate the aminium radical generated by SET, since the pKa has been estimated to be approximately 9. Dihydropyridine aminium radicals have low pKa (< 4) and are generally considered to have considerable kinetic acidity. None of the haemoproteins under consideration (including the peroxidases and haemoglobin) showed high kinetic hydrogen isotope effects for the oxidation of [4-2H]- or [4-3H]-labelled 1,4-dihydropyridines. These results are consonant with the view that P450s catalyse the deprotonation of N,N-dialkylaniline aminium radicals. 4. Since low isotope effects were seen with biomimetic metalloporphyrin models as well as P450s, the deprotonation is attributed to the (FeO)2+ entity, expected to be a strong base, and not the apoprotein. Thus, the FeO moiety of peroxidases is shielded, consistent with evidence by others that SET occurs through the porphyrin edge. Both P450s and peroxidases catalysed the oxidative N-demethylation of aminopyrine and N,N-dimethylaminothioanisole; however, only the peroxidases generated the stable coloured aminium radicals. 5. The rates of N-demethylation of variously para-substituted N,N-dimethylanilines can be used to undertake Hammett or Marcus analysis. The former yields rho = -0.6 and the latter an apparent E1/2 of approximately 1.8 for the formal (FeO)3+ entity of P4502B1. 6. Even in the oxidation of N,N-dialkylanilines, a finite rate of N-oxidation is seen (approximately 0.1% of N-dealkylation). The simplest paradigm has N-oxygenation and N-dealkylation both proceeding from a common aminium radical intermediate.
Collapse
Affiliation(s)
- F P Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | | | | | | |
Collapse
|
20
|
Brady JF, Wang MH, Hong JY, Xiao F, Li Y, Yoo JS, Ning SM, Lee MJ, Fukuto JM, Gapac JM. Modulation of rat hepatic microsomal monooxygenase enzymes and cytotoxicity by diallyl sulfide. Toxicol Appl Pharmacol 1991; 108:342-54. [PMID: 2017758 DOI: 10.1016/0041-008x(91)90123-v] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Diallyl sulfide (DAS) and other organosulfur compounds inhibit chemically induced carcinogenic and toxic responses in rodent model systems. A possible mechanism of action is the inhibition of the hepatic cytochrome P450IIE1-dependent bioactivation of the procarcinogens and protoxicants. Previous work showed competitive inhibition by DAS of N-nitrosodimethylamine (NDMA) demethylase activity in vitro, and a reduction in the microsomal level of P450IIE1 after in vivo treatment with DAS. The present studies demonstrated a time- and dose-dependent decrease of hepatic microsomal P450IIE1 activity, induction of P450IIB1 and pentoxyresorufin dealkylase activity, and moderate induction of ethoxyresorufin dealkylase activity by oral DAS treatment. DAS treatment elevated P450IIB1 mRNA but had no effect on P450IIE1 mRNA. Treatment with putative metabolites of DAS, diallyl sulfoxide and diallyl sulfone, led to similar modulations in monooxygenase activities, but the decrease of P450IIE1 activity by the sulfone occurred more rapidly. In studies in vitro, diallyl sulfone caused a metabolism-dependent inactivation of P450IIE1, but such inactivation was not observed with DAS or diallyl sulfoxide. The profile of microsomal testosterone metabolism after DAS treatment indicated an enhancement of P450IIB1-dependent 16 beta-hydroxylase activity, and a decrease in 6 beta-hydroxytestosterone production possibly related to a lower level of P450IIIA1 or IIIA2. When rats were subjected to a 48-hr fast and DAS treatment, the starvation-induced microsomal P450IIE1 level was decreased by DAS. Inhibition of hepatotoxicity due to exposure to P450IIE1 substrates, CCl4 and NDMA, by DAS was observed under a variety of treatment schedules.
Collapse
Affiliation(s)
- J F Brady
- Department of Chemical Biology and Pharmacognosy, College of Pharmacy, Rutgers University, Piscataway, New Jersey 08855-0789
| | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Hvattum E, Bergseth S, Pedersen CN, Bremer J, Aarsland A, Berge RK. Microsomal oxidation of dodecylthioacetic acid (a 3-thia fatty acid) in rat liver. Biochem Pharmacol 1991; 41:945-53. [PMID: 1672593 DOI: 10.1016/0006-2952(91)90200-o] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
[1-14C]Dodecylthioacetic acid (DTA), a 3-thia fatty acid, is omega (omega-1)-hydroxylated and sulfur oxygenated at about equal rates in rat liver microsomes. In prolonged incubations DTA is converted to omega-hydroxydodecylsulfoxyacetic acid. omega-Hydroxylation of DTA is catalysed by cytochrome P450IVA1 (or a very closely related isoenzyme in the same gene family), the fatty acid omega-hydroxylating enzyme. It is absolutely dependent on NADPH and inhibited by CO, and lauric acid is a competing substrate. omega-Hydroxylation of DTA is increased by feeding tetradecylthioacetic acid (TTA), a 3-thia fatty acid, for 4 days to rats. omega-Hydroxylation of [1-14C]lauric acid is also induced by TTA and other 3-thia carboxylic acids. A close relationship was observed between induction of microsomal omega-hydroxylation of fatty acid and palmitoyl-CoA hydrolase activity. DTA is omega-hydroxylated at about the same rate as the physiological substrate lauric acid. The sulfur oxygenation of DTA is catalysed by liver microsomal flavin-containing monooxygenase (FMO) (EC 1.14.13.8). It is dependent on either NADH or NADPH. The Km value for NADH was approx. five times larger than the Km value for NADPH. It is inhibited by methimazole and not affected by CO. It is not induced by TTA.
Collapse
Affiliation(s)
- E Hvattum
- Institute of Medical Biochemistry, University of Osló, Norway
| | | | | | | | | | | |
Collapse
|
22
|
Bergseth S, Bremer J. Alkylthioacetic acids (3-thia fatty acids) are metabolized and excreted as shortened dicarboxylic acids in vivo. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1044:237-42. [PMID: 2344442 DOI: 10.1016/0005-2760(90)90308-k] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The metabolism of 1-14C-labeled long-chain alkylthioacetic acids (3-thia fatty acids) which are blocked for normal beta-oxidation by a sulfur atom in the beta-position has been investigated in vivo. Most of the injected radioactivity (greater than 50%) was excreted in the urine within the first 48 h. The recovered and identified metabolites were all short sulfoxydicarboxylic acids. The main metabolite from dodecylthioacetic acid was carboxypropylsulfoxy acetic acid. Some bis(carboxymethyl)sulfoxide (dithioglycolic acid sulfoxide) was also found. The main metabolite from nonylthioacetic acid was carboxyethylsulfoxyacetic acid. No sulfones were found. Less than 1% of the 1-14C from the dodecylthioacetic acid was recovered in respiratory CO2 and about 3% of the 1-14C from nonylthioacetic acid. [1-14C]Dodecyl-sulfonylacetic acid was recovered almost quantitatively as carboxypropylsulfonylacetic acid in the urine after 3 h. A significant fraction (10% of the dodecylthioacetic acid was recovered in the phospholipids and triacylglycerols from liver and epidymal fat pad 4 h after injection. These experiments show that the alkylthioacetic acids undergo an initial omega-oxidation followed by beta-oxidation to short dicarboxylic acids.
Collapse
Affiliation(s)
- S Bergseth
- University of Oslo, Institute of Medical Biochemistry, Norway
| | | |
Collapse
|
23
|
Abstract
Studies with biomimetic models can yield considerable insight into mechanisms of enzymatic catalysis. The discussion above indicates how such information has been important in the cases of flavoproteins, hemoproteins, and, to a lesser extent, the copper protein dopamine beta-hydroxylase. Some of the moieties that we generally accept as intermediates (i.e., high-valent iron oxygen complex in cytochrome P-450 reactions) would be extremely hard to characterize were it not for biomimetic models and more stable analogs such as peroxidase Compound I complexes. Although biomimetic models can be useful, we do need to keep them in perspective. It is possible to alter ligands and aspects of the environment in a way that may not reflect the active site of the protein. Eventually, the model work needs to be carried back to the proteins. We have seen that diagnostic substrates can be of considerable use in understanding enzymes and examples of elucidation of mechanisms through the use of rearrangements, mechanism-based inactivation, isotope labeling, kinetic isotope effects, and free energy relationships have been given. The point should be made that a myriad of approaches need to be applied to the study of each enzyme, for there is potential for misleading information if total reliance is placed on a single approach. The point also needs to be made that in the future we need information concerning the structures of the active sites of enzymes in order to fully understand them. Of the enzymes considered here, only a bacterial form of cytochrome P-450 (P-450cam) has been crystallized. The challenge to determine the three-dimensional structures of these enzymes, particularly the intrinsic membrane proteins, is formidable, yet our further understanding of the mechanisms of enzyme catalysis will remain elusive as long as we have to speak of putative specific residues, domains, and distances in anecdotal terms. The point should be made that there is actually some commonality among many of the catalytic mechanisms of oxidation, even among proteins with different structures and prosthetic groups. Thus, we see that cytochrome P-450 has some elements of a peroxidase and vice versa; indeed, the chemistry at the prosthetic group is probably very similar and the overall chemistry seems to be induced by the protein structure. The copper protein dopamine beta-hydroxylase appears to proceed with chemistry similar to that of the hemoprotein cytochrome P-450 and, although not so thoroughly studied, the non-heme iron protein P. oleovarans omega-hydroxylase.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
|
24
|
el Amri HS, Fargetton X, Delatour P, Batt AM. Sulphoxidation of albendazole by the FAD-containing and cytochrome P-450 dependent mono-oxygenases from pig liver microsomes. Xenobiotica 1987; 17:1159-68. [PMID: 3424864 DOI: 10.3109/00498258709167408] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
1. Two distinct microsomal pathways involved in the metabolism of albendazole (ABZ) to albendazole-sulphoxide (SO.ABZ) by pig liver microsomes have been identified and quantified. 2. The binding of ABZ to microsomal cytochrome P-450 (Type I spectrum, Ks = 25.5 microM), the decrease of the rate of sulphoxidation by antibody against NADPH cytochrome c reductase, and the use of purified cytochrome P-450 A demonstrated the contribution of a cytochrome P-450-dependent mono-oxygenase to the metabolism of ABZ. 3. The involvement of FAD-containing mono-oxygenase (FMO) was shown by thermal pretreatment of microsomes, n-octylamine activation of the reaction, and by using purified pig liver FMO. 4. From Km and Vmax values, it would appear that the relative contributions of the two systems depend on the concentration of ABZ.
Collapse
Affiliation(s)
- H S el Amri
- Centre du Médicament, U.A. C.N.R.S., Nancy, France
| | | | | | | |
Collapse
|
25
|
Kinetic solvent deuterium isotope effect on the oxygenation of N,N-dimethylaniline with the pig liver microsomal fad-containing monooxygenase. Tetrahedron Lett 1986. [DOI: 10.1016/s0040-4039(00)84210-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|