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Abstract
The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.
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Affiliation(s)
- Patrick E Hanna
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN, USA
| | - M W Anders
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, USA
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2
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Abstract
Over the years, numerous studies have supported the premise that individuals possessing the "slow acetylator" phenotype are more at risk from developing drug side-effects. Most prominent amongst these reports are those concerned with hepatotoxicity and peripheral neuropathy following treatment with isoniazid, lupus-like symptoms during procainamide therapy and experiencing hypersensitivity reactions to the various sulphonamide derivatives. Similarly, "slow acetylators" undergoing heavy exposure to arylamines and related carcinogens are more likely to develop bladder cancer. Contrariwise, there appears a slight risk of "rapid acetylators" developing pancreatic tumours.Other therapeutic agents for which polymorphic N-acetylation plays a minor role in their metabolism have been investigated but any impact of this metabolic difference on clinical efficacy or associated toxicity is still under question. In the search for clues as to the underlying aetiology, patient groups with many disease states have been examined for association with differences in N-acetylation and the majority have provided data that could be interpreted as equivocal. Studies have given contradictory, often opposing, results, calculated risk factors that are (perhaps) just significant but certainly not high, and patients within the cohorts who are always exceptions. Undoubtedly, other as yet unappreciated factors are at play.
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Affiliation(s)
- Stephen C Mitchell
- Section of Computational and Systems Medicine, Faculty of Medicine, Imperial College London, London, UK
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3
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Abstract
The biochemical facets of toxicology have always had a major role in providing insight into mechanisms. Some of the history of the development of this area is summarized, including metabolism, enzymology, and the chemistry of reactive intermediates. Knowledge in these fields has had a major impact in the areas of drug metabolism and safety assessment, which are both critical steps in the development of pharmaceuticals and the rational use of commodity chemicals. The science of toxicology has developed considerably with input from other disciplines and today is poised to emerge as a predictive science with even more dramatic impact. The challenges ahead are considerable but there is renewed excitement in the potential of the field. As in the past, further advances in the field of toxicology will require the input of knowledge from many disciplines.
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Affiliation(s)
- F Peter Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
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4
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Enrichment and properties of urinary pre-S-phenylmercapturic acid (pre-SPMA). J Chromatogr B Analyt Technol Biomed Life Sci 2010; 878:2502-5. [DOI: 10.1016/j.jchromb.2009.08.043] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Revised: 07/17/2009] [Accepted: 08/31/2009] [Indexed: 11/23/2022]
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5
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Hanzlik RP, Fang J, Koen YM. Filling and mining the reactive metabolite target protein database. Chem Biol Interact 2008; 179:38-44. [PMID: 18823962 DOI: 10.1016/j.cbi.2008.08.016] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2008] [Revised: 08/22/2008] [Accepted: 08/26/2008] [Indexed: 12/13/2022]
Abstract
The post-translational modification of proteins is a well-known endogenous mechanism for regulating protein function and activity. Cellular proteins are also susceptible to post-translational modification by xenobiotic agents that possess, or whose metabolites possess, significant electrophilic character. Such non-physiological modifications to endogenous proteins are sometimes benign, but in other cases they are strongly associated with, and are presumed to cause, lethal cytotoxic consequences via necrosis and/or apoptosis. The Reactive Metabolite Target Protein Database (TPDB) is a searchable, freely web-accessible (http://tpdb.medchem.ku.edu:8080/protein_database/) resource that attempts to provide a comprehensive, up-to-date listing of known reactive metabolite target proteins. In this report we characterize the TPDB by reviewing briefly how the information it contains came to be known. We also compare its information to that provided by other types of "-omics" studies relevant to toxicology, and we illustrate how bioinformatic analysis of target proteins may help to elucidate mechanisms of cytotoxic responses to reactive metabolites.
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Affiliation(s)
- Robert P Hanzlik
- Department of Medicinal Chemistry and Bioinformatics Core Facility, University of Kansas, Lawrence, 66045-7582, USA.
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6
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Mannervik B. The isoenzymes of glutathione transferase. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 57:357-417. [PMID: 3898742 DOI: 10.1002/9780470123034.ch5] [Citation(s) in RCA: 194] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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7
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Boyland E, Chasseaud LF. The role of glutathione and glutathione S-transferases in mercapturic acid biosynthesis. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 32:173-219. [PMID: 4892500 DOI: 10.1002/9780470122778.ch5] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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8
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Caldwell J. Drug metabolism and pharmacogenetics: the British contribution to fields of international significance. Br J Pharmacol 2006; 147 Suppl 1:S89-99. [PMID: 16402125 PMCID: PMC1760745 DOI: 10.1038/sj.bjp.0706466] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The branch of pharmacology we now call 'drug metabolism', the consideration of the enzymes and procesess determining the disposition of drugs in the body, emerged in the 1840s on the continent of Europe, but British science made little or no contribution until the 1920s. From this point on, the development of the field through the 20th century was shaped to a very significant extent by a series of influential British workers, whose contributions were of global significance and who can now be seen as fathers of the subject. Since the 1950s, and gaining pace inexorably from the 1970s, the significance of drug metabolism to human therapeutics has been greatly added to by the emergence of pharmacogenetics, clinically important hereditary variation in response to drugs, which underpins the current emphasis on personalised medicine. This review examines the British contributions to both these fields through the lives of seven key contributors and attempts to place their work both in the context of its time and its lasting influence.
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Affiliation(s)
- John Caldwell
- Faculty of Medicine, The University of Liverpool, Duncan Building, Daulby Street, Liverpool L69 3GA.
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9
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Arteel GE, Sies H. The biochemistry of selenium and the glutathione system. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2001; 10:153-158. [PMID: 21782571 DOI: 10.1016/s1382-6689(01)00078-3] [Citation(s) in RCA: 196] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In the context of defense against pro-oxidants, selenium and the glutathione (GSH) system play key functions. Major roles of GSH include direct interception of pro-oxidants, as well as a reduction of other antioxidants from their oxidized forms. Furthermore, GSH has ancillary functions, such as metabolism, cell signaling, and protein interactions, that can also mediate defense against oxidants. Protection by selenium in the mammalian cell is mediated by selenol-aminoacids, either as selenocysteine or selenomethionine. The active site of the potent glutathione peroxidases (GPx) contains selenocysteine residues. Furthermore, other selenoproteins (e.g. selenoprotein P and thioredoxin reductase) also have been shown to possess antioxidant properties. Synthetic organoselenium compounds (e.g. ebselen) have also shown promise as pharmacologic antioxidants in in vivo models of tissue damage due to oxidative stress. The specific function of selenoproteins and organoselenium compounds in defense against peroxynitrite, by reduction of this potent oxidizing and nitrating species to nitrite, is also discussed.
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Affiliation(s)
- G E Arteel
- Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, CB #7365 Mary Ellen Jones Building, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
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10
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Abstract
Metabolism plays important roles in chemical carcinogenesis, both good and bad. The process of carcinogen metabolism was first recognized in the first half of the twentieth century and developed extensively in the latter half. The activation of chemicals to reactive electrophiles that become covalently bound to DNA and protein was demonstrated by Miller and Miller [Cancer 47 (1981) 2327]. Today many of the DNA adducts formed by chemical carcinogens are known, and extensive information is available about pathways leading to the electrophilic intermediates. Some concepts about the stability and reactivity of electrophiles derived from carcinogens have changed over the years. Early work in the field demonstrated the ability of chemicals to modulate the metabolism of carcinogens, a phenomenon now described as enzyme induction. The cytochrome P450 enzymes play a prominent role in the metabolism of carcinogens, both in bioactivation and detoxication. The conjugating enzymes can also play both beneficial and detrimental roles. As an example of a case in which several enzymes affect the metabolism and carcinogenicity of a chemical, aflatoxin B1 (AFB1) research has revealed insight into the myriad of reaction chemistry that can occur even with a 1s half-life for a reactive electrophile. Further areas of investigation involve the consequences of enzyme variability in humans and include areas such as genomics, epidemiology, and chemoprevention.
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Affiliation(s)
- F P Guengerich
- Department of Biochemistry, Center of Molecular Toxicology, Vanderbilt University School of Medicine, 638 Medical Research Building I, 23rd Avenue South at Pierce, Nashville, TN 37232-0146, USA.
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11
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Abstract
Glutathione (GSH) is the major cellular thiol participating in cellular redox reactions and thioether formation. This article serves as introduction to the FRBM Forum on glutathione and emphasizes cellular functions: What is GSH? Where does it come from? Where does it go? What does it do? What is new and noteworthy? Research tools, historical remarks, and links to current trends.
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Affiliation(s)
- H Sies
- Institut für Physiologische Chemie I, Heinrich-Heine-Universität Düsseldorf, Germany.
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12
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Affiliation(s)
- G J Beckett
- University Department of Clinical Biochemistry, Royal Infirmary, Edinburgh, Scotland
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13
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van Welie RT, van Dijck RG, Vermeulen NP, van Sittert NJ. Mercapturic acids, protein adducts, and DNA adducts as biomarkers of electrophilic chemicals. Crit Rev Toxicol 1992; 22:271-306. [PMID: 1489508 DOI: 10.3109/10408449209146310] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The possibilities and limitations of using mercapturic acids and protein and DNA adducts for the assessment of internal and effective doses of electrophilic chemicals are reviewed. Electrophilic chemicals may be considered as potential mutagens and/or carcinogens. Mercapturic acids and protein and DNA adducts are considered as selective biomarkers because they reflect the chemical structure of the parent compounds or the reactive electrophilic metabolites formed during biotransformation. In general, mercapturic acids are used for the assessment of recent exposure, whereas protein and DNA adducts are used for the assessment of semichronic or chronic exposure. 2-Hydroxyethyl mercapturic acid has been shown to be the urinary excretion product of five different reactive electrophilic intermediates. Classification of these electrophiles according to their acid-base properties might provide a tool to predict their preference to conjugate with either glutathione and proteins or with DNA. Constant relationships appear to exist in the cases of 1,2-dibromoethane and ethylene oxide between urinary mercapturic acid excretion and DNA and protein adduct concentrations. This suggests that mercapturic acids in some cases may also play a role as a biomarker of effective dose. It is concluded that simultaneous determination of mercapturic acids, protein and DNA adducts, and other metabolites can greatly increase our knowledge of the specific roles these biomarkers play in internal and effective dose assessment. If the relationship between exposure and effect is known, similar to protein and DNA adducts, mercapturic acids might also be helpful in (individual) health risk assessment.
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Affiliation(s)
- R T van Welie
- Department of Pharmacochemistry, Vrije Universiteit, Amsterdam, The Netherlands
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14
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Meister A. Glutathione deficiency produced by inhibition of its synthesis, and its reversal; applications in research and therapy. Pharmacol Ther 1991; 51:155-94. [PMID: 1784629 DOI: 10.1016/0163-7258(91)90076-x] [Citation(s) in RCA: 651] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Glutathione, which is synthesized within cells, is a component of a pathway that uses NADPH to provide cells with their reducing milieu. This is essential for (a) maintenance of the thiols of proteins (and other compounds) and of antioxidants (e.g. ascorbate, alpha-tocopherol), (b) reduction of ribonucleotides to form the deoxyribonucleotide precursors of DNA, and (c) protection against oxidative damage, free radical damage, and other types of toxicity. Glutathione interacts with a wide variety of drugs. Despite its many and varied cellular functions, it is possible to achieve therapeutically useful modulations of glutathione metabolism. This article emphasizes an approach in which the synthesis of glutathione is selectively inhibited in vivo leading to glutathione deficiency. This is achieved through use of transition-state inactivators of gamma-glutamylcysteine synthetase, the enzyme that catalyzes the first and rate-limiting step of glutathione synthesis. The effects of marked glutathione deficiency, thus produced in the absence of applied stress, include cellular damage associated with severe mitochondrial degeneration in a number of tissues. Such glutathione deficiency is not prevented or reversed by giving glutathione. The cellular utilization of GSH involves its extracellular degradation, uptake of products, and intracellular synthesis of GSH. This is a normal pathway by which cysteine moieties are taken up by cells. Glutathione deficiency induced by inhibition of its synthesis may be prevented or reversed by administration of glutathione esters which, in contrast to glutathione, are readily transported into cells and hydrolyzed to form glutathione intracellularly. Research derived from this model has led to several potentially useful therapeutic approaches, one of which is currently in clinical trial. Thus, certain tumors, including those that exhibit resistance to several drugs and to radiation, are sensitized to these modalities by selective inhibition of glutathione synthesis. An alternative interpretation is suggested which is based on the concept that some resistant tumors have high capacity for glutathione synthesis and that such increased capacity may be as significant or more significant in promoting the resistance of some tumors than the cellular levels of glutathione. Therapeutic approaches are proposed in which normal cells may be selectively protected against toxic antitumor agents and radiation by cysteine- and glutathione-delivery compounds. Current studies suggest that research on other modulations of glutathione metabolism and transport would be of interest.
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Affiliation(s)
- A Meister
- Department of Biochemistry, Cornell University Medical College, New York, NY 10021
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15
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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)
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16
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Clonfero E, Zordan M, Venier P, Paleologo M, Levis AG, Cottica D, Pozzoli L, Jongeneelen FJ, Bos RP, Anzion RB. Biological monitoring of human exposure to coal tar. Urinary excretion of total polycyclic aromatic hydrocarbons, 1-hydroxypyrene and mutagens in psoriatic patients. Int Arch Occup Environ Health 1989; 61:363-8. [PMID: 2744865 DOI: 10.1007/bf00381025] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Three methods for the biological monitoring of human exposure to coal tar were compared. Levels of 1-hydroxypyrene(1-OH PYR), polycyclic aromatic hydrocarbons (PAH) and mutagens (Ames plate incorporation assay using Salmonella typhimurium strain TA98 in the presence of S9 and beta-glucuronidase) were determined in urinary samples from psoriatic patients undergoing topical treatment with mineral coal tar. A single sample of urine with a high content of PAH was diluted with urine of nonexposed, non-smoking subjects in order to obtain nine samples with a decreasing content of PAh metabolites. Mutagenicity of the extracts was detectable down to the dilution corresponding to a content in 1-OH PYR of about 50 micrograms/g creatinine and total PAH of 7 micrograms/g creatinine. In a second phase the three indicators of exposure to PAH were compared in 16 urinary samples from four psoriatic patients. The total PAH levels determined by the acidic deconjugation/reduction method were confirmed to be nearly always lower than the corresponding levels of 1-OH PYR alone. Most of the extracts were mutagenic, however, some of the samples with a high content in PAh metabolites were not mutagenic. In all the urinary samples analyzed the excretion of 1-OH PYR was markedly greater than in control subjects. 1-OH PYR and urinary mutagenicity levels were well correlated. The present data suggest that both the determination of mutagenicity and 1-OH PYR in urine may be used to monitor occupational exposure to PAH, the latter method being cheaper and of greater specificity and sensitivity.
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Affiliation(s)
- E Clonfero
- Institute of Occupational Health, University of Padua, Italy
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17
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Sies H. [Biochemistry of thiol groups: the role of glutathione]. THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 1989; 76:57-64. [PMID: 2657438 DOI: 10.1007/bf00396705] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Glutathione (GSH) comprises the bulk of the pool of free thiol groups in biological systems. Since its first description as philothione 100 years ago, there have been repeated surprises in discoveries of novel functions. Just recently the important role of thioethers with products of the lipoxygenase reaction, i.e., the leukotrienes, was revealed as mediator of physiological and pathophysiological processes. Another major function resides in detoxication, GSH being cosubstrate in the GSH-peroxidase reaction for the reduction of hydroperoxides in the defense against oxidative stress. Interest also focuses on reactions of glutathionyl radicals in protection by thiols against DNA damage resulting from ionizing radiation.
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Affiliation(s)
- H Sies
- Institut für Physiologische Chemie I der Universität, Düsseldorf
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18
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Toyo'oka T, Suzuki T, Saito Y, Takahashi A. Electrochemical detection of mercapturic acid derivatives after separation by high-performance liquid chromatography. J Chromatogr A 1989. [DOI: 10.1016/s0021-9673(01)89693-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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19
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Schäffer J, Gallay O, Ladenstein R. Glutathione transferase from bovine placenta. Preparation, biochemical characterization, crystallization, and preliminary crystallographic analysis of a neutral class PI enzyme. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)77850-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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20
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James SP. The biochemistry of endogenous organosulphur compounds. DRUG METABOLISM AND DRUG INTERACTIONS 1988; 6:167-82. [PMID: 3155361 DOI: 10.1515/dmdi.1988.6.3-4.167] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The role and metabolism of methionine and cysteine in mammals are described. An outline of the history of glutathione, of its function in maintaining the thiol status of the cell and of its protective action against oxidative stress, is given. The importance of glutathione reductase, glutathione peroxidases, glutathione-S-transferases in endogenous metabolism and of gamma-glutamyltranspeptidase is described. The relationship between cysteine and glutathione is considered together with the inter-organ translocation of glutathione and its metabolism.
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Affiliation(s)
- S P James
- School of Biochemistry, University of Birmingham, UK
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21
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Abstract
Aerobic organisms by definition require oxygen, and the importance of iron in aerobic respiration has long been recognized, but despite their beneficial roles, these elements can pose a real threat to the organism. During oxygen reduction, reactive species such as O2-. and H2O2 are formed readily. Iron can combine with these species, or with molecular oxygen itself, to generate free radicals which will attack the polyunsaturated fatty acids of membrane lipids. This oxidative deterioration of membrane lipids is known as lipid peroxidation. To protect itself against this form of attack, the organism possesses several types of defense mechanisms. Under normal conditions, these defenses appear to offer adequate protection for cell membranes, but the possibility exists that certain foreign compounds may interfere with or even overwhelm these defenses, and herein could lie a general mechanism of toxicity. This possible cause of toxicity is discussed in relation to other suggested causes.
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Affiliation(s)
- A A Horton
- Department of Biochemistry, University of Birmingham, England
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22
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Scherer G, Westphal K, Biber A, Hoepfner I, Adlkofer F. Urinary mutagenicity after controlled exposure to environmental tobacco smoke (ETS). Toxicol Lett 1987; 35:135-40. [PMID: 3544340 DOI: 10.1016/0378-4274(87)90098-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
20 non-smokers on a defined diet low in polycyclic aromatic hydrocarbons (PAH) were exposed to environmental tobacco smoke (ETS) in an unventilated room for 8 h. The urinary mutagenicity in the 24-h urine samples as tested with the Salmonella (TA98) microsome assay did not significantly increase after exposure to either 10 ppm CO or 20-25 ppm CO. We conclude that exposure of non-smokers to ETS does not lead to an increase in their urinary mutagenicity, provided the exposure conditions are within a realistic range.
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Beyhl FE, Mayer DG. Studies on liver toxicants: influence of bromobenzene on hepatic microsomal enzymes in mice. Toxicol Lett 1981; 7:481-5. [PMID: 6787742 DOI: 10.1016/0378-4274(81)90097-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The effect of acute bromobenzene intoxication on drug-metabolizing liver enzymes was studied. After an oral dose of 3000 mg/kg body weight of bromobenzene, the glucuronyltransferases I and II were increased, indicating an enzyme activation by this organic solvent via membrane irritation. The mixed-function oxidases were inhibited with the exception of the ketamine N-demethylase. Microsomal lipoperoxidation was reduced whilst H2O2 formation was unchanged.
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Abstract
Epidemiological studies have shown that those who work in rubber industry have an increased risk of cancer. In the working environment they are exposed, probably, to several hundred different chemicals some of them being known or suspected carcinogens and mutagens. The bacterial fluctuation test was used to detect the mutagenicity in the urines of exposed workers. A group of unexposed office clerks served as controls. Both groups consisted of smokers and non-smokers, and that was taken into consideration in the results. Rubber workers, either smokers or non-smokers, exhibited significantly higher mutagenic activity in their urine than the occupationally unexposed controls when the base-pair substitution strain E. coli WP2 uvrA was used as indicator organism. Use of the frameshift strain S. typhimurium TA98 revealed increased mutagenicity in the urine of occupationally exposed smokers, nonsmokers and unexposed smokers. The extent of mutagenicity in the urine of workers who smoked suggested a synergistic effect of smoking and occupational exposure. The bacterial fluctuation test with urine samples as sources of mutagenicity is able to detect chemical exposure if the excreted compounds are still in active form or can be activated. The method can be used to identify hazardous working conditions long before the manifestation of possible pathological changes in exposed individuals.
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Beyhl FE, Mayer DG. Studies on liver toxicants. Influence of bromobenzene on hepatic microsomal enzymes in rats. Arch Toxicol 1980; 43:257-62. [PMID: 6770795 DOI: 10.1007/bf00366181] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In acute oral studies, the effect of bromobenzene on hepatic microsomal enzymes was investigated. Neither glucuronyltransferases nor cytochrome c reductase showed significant changes. Most of the mixed-function oxidases studied were inhibited with the exception of ketamine-N-demethylase. The data indicate that bromobenzene or its epoxide acts on cytochrome P-450 but not on all cytochrome P-450 species, and does not affect the reductase and the glucuronyltransferases. Microsomal lipoperoxidation and microsomal H2O2 formation were increased.
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30
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Abstract
1. The metabolism of several dihalopropanols has been studied in the rat. Irrespective of their structure, each compound produced the same two mercapturic acids, excreted as urinary metabolites. 2. The mercapturic acid metabolites of the dihalopropanols were identified as N-acetyl-S-(2,3-dihydroxypropyl)cysteine and N,N'-bis-acetyl-S,S'-(1,3-bis-cysteinyl)propan-2-ol. Depending on the halogen present, each dihalopropanol produced beta-chlorolactate or beta-bromolactate as oxidative metabolites. 3. From the metabolic pathway of these compounds, it is inferred that an epoxide is an intermediate in their metabolism. 4. The metabolism of 2-chloropropane-1,3-diol has been investigated in the rat and the isolation of one mercapturic acid, N-acetyl-S-(2,3-dihydroxypropyl)cysteine, confirms that an epoxide intermediate is involved.
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31
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Chasseaud LF. The role of glutathione and glutathione S-transferases in the metabolism of chemical carcinogens and other electrophilic agents. Adv Cancer Res 1979; 29:175-274. [PMID: 474272 DOI: 10.1016/s0065-230x(08)60848-9] [Citation(s) in RCA: 849] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Vainio H, Savolainen H, Kilpikari I. Urinary thioether of employees of a chemical plant. BRITISH JOURNAL OF INDUSTRIAL MEDICINE 1978; 35:232-234. [PMID: 698138 PMCID: PMC1008411 DOI: 10.1136/oem.35.3.232] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The thiols in the morning urine of 224 employees of a chemical plant were determined after alkaline hydrolysis of all urinary thioethers. The highest thioether excretion was found in rubber workers and radial tyre builders in comparison with clerks, plastic monomer mixers and footwear preparers. Smoking and medication tended to increase thioether excretion. Urinary thioether determination may prove to be a valuable tool in assessing exposure to mixtures of chemicals regardless of the route of absorption.
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Chasseaud LF. The nature and distribution of enzymes catalyzing the conjugation of glutathione with foreign compounds. Drug Metab Rev 1974; 2:185-220. [PMID: 4369329 DOI: 10.3109/03602537409030009] [Citation(s) in RCA: 139] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Reid WD, Krishna G. Centrolobular hepatic necrosis related to covalent binding of metabolites of halogenated aromatic hydrocarbons. Exp Mol Pathol 1973; 18:80-99. [PMID: 4693627 DOI: 10.1016/0014-4800(73)90009-9] [Citation(s) in RCA: 96] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Daly JW, Jerina DM, Witkop B. Arene oxides and the NIH shift: the metabolism, toxicity and carcinogenicity of aromatic compounds. EXPERIENTIA 1972; 28:1129-49. [PMID: 4117670 DOI: 10.1007/bf01946135] [Citation(s) in RCA: 516] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Jerina D, Daly J, Witkop B, Zaltzman-Nirenberg P, Udenfriend S. Role of the arene oxide-oxepin system in the metabolism of aromatic substrates. Arch Biochem Biophys 1968. [DOI: 10.1016/0003-9861(68)90020-9] [Citation(s) in RCA: 189] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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West H, Mathura G, Black L. LABORATORY SYNTHESIS OF p-CHLOROPHENYL-l-CYSTEINE AND ITS ACETYLATION BY THE RAT. J Biol Chem 1951. [DOI: 10.1016/s0021-9258(19)52435-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Lang K. Über die Einwirkung organischer Fluorverbindungen auf den tierischen Organismus. Naunyn Schmiedebergs Arch Pharmacol 1930. [DOI: 10.1007/bf01862866] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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