GLUTATHIONE S-TRANSFERASES: A BRIEF ON CLASSIFICATION AND GSTM1-T1 ACTIVITY

GLUTATHIONE S-TRANSFERASES: A BRIEF ON CLASSIFICATION AND GSTM1-T1 ACTIVITY

Prem Chandra Suthar ^{1, 2}

Anthropological Survey of India ¹, Western Regional Centre, Udaipur -313001, Rajasthan, India.

Faculty of Science ², Pacific Academy of Higher Education and Research University, Udaipur, Rajasthan, India -313003.

ABSTRACT: The glutathione S-transferase (GST) isoenzyme superfamilies detoxify a wide-range of toxic chemicals and environmental substances are extensively expressed in mammalian tissues. Liver and pancreas are the sites where cytosolic Phase I and phase II biotransformation GSTs enzymes have characteristic expression. GSTs play a key role in the deactivation of reactive oxygen species (ROS) and the metabolism of lipids, chemotherapeutic agents. GSTs are mainly involved in conjugation of reduced glutathione (GSH) with diverse substrates specificity and it is possible that genetic variations in these enzymes will influence cellular response to the environmental agents. GSTs are overexpressed in response to a chemical or oxidative stress as an adaptive physiology and upregulated in cancerous state of organ or tissue. GSTs are essentially involved in susceptibility to various forms of cancer as they are vital in detoxification mechanism to metabolize the environmental carcinogens. GSTM1 encodes for a class mu GST isoenzyme involved in polycyclic aromatic hydrocarbons (PAHs) detoxification. The substrates of GSTM1 include benzo(a)pyrene, benzo(c)phenanthrene, benzo(g)chrysene and other carcinogens. They can catalyze in-vitro GSH conjugation with several potent carcinogenic epoxides including aflatoxin B1(AFB1)8,9-epoxide and electrophilic metabolites of PAHs present in tobacco smoke. Ethylene dibromide, p-nitrobenzyl chloride, p-nitrophenetyl bromide, methyl chloride, and methyl iodide, are known substrates for GSTT1 or GST Theta (θ). GST Theta is most primitive among other known GSTs and widely expressed in nature.

Glutathione S-Transferase, Toxic Chemicals, Oxidative Stress, Class, GSTM1, GSTT1, Biotransformation

INTRODUCTION: The glutathione S-transferase gene family encodes genes for detoxification mechanisms. GST play an inimitable role in biotransformation of drugs and detoxify a number of endogenous and exogenous electrophilic lipophiles. ¹ In response to a chemical or oxidative stress or they are overexpressed as a part of adaptive mechanism and upregulated during cancerous state.

GSTs are essentially involved in susceptibility to various forms of cancer as they are vital in detoxification mechanism to handle the environmental carcinogens. ² GST is involved in conjugation of reduced glutathione (GSH) with diverse substrates and it is possible that genetic variations in these enzymes will influence cellular response to the environmental agents. Also GST super families exhibit some redundancy i.e. the overlap in substrate specificity of individual isoenzymes. ³ The active soluble cytosolic GSTs enzyme exists as a dimeric protein of two subunits approximately 25 kDa. ^{4, 5} The GSH-binding and the hydrophobic substrate-binding sites have been called the G- and H-sites, respectively. ⁶

1-chloro-2, 4-dinitrobenzene (CDNB) is a universal substrate of GST and they are able to catalyze conjugation of reduced glutathione (GSH) with the aryl halides, 1,2-dichloro-4-nitrobenzene and bromosulfophthalein. ^{7, 8} GSTs also conjugate isothiocyanates, which are potent inducers of enzymes that detoxify environmental mutagens. ⁹ The conjugation process diverts the isothiocyanates from the enzyme induction pathway into excretion, leading to elimination of these anticarcinogenic substances and thus decreasing their potential chemopreventive effect. ^{10, 11, 12} They may also play a role in the metabolism of lipids, chemotherapeutic agents and reactive oxygen species.¹³

Classification of GSTs: The glutathione S-transferases (EC 2.5.1.18) are isoenzymes superfamilies that detoxify toxic substances are widely distributed in nature. ^{14, 15} Classified under two distinct categories, the larger superfamily include cytosolic, soluble, dimeric enzymes that are involved in biotransformation of toxic xenobiotics and endobiotics. ^{16, 17, 18, 19, 20} The other superfamily involves microsomal GST probably trimeric in structure and known as membrane-associated proteins in eicosanoid and glutathione (MAPEG) metabolism, primarily involved in arachidonic acid metabolism. ²¹

On the basis of their primary structure the human cytosolic/soluble GST superfamily contains at least 16 genes subdivided into eight separate classes designated α(GSTA), mu(GSTM), π(GSTP), θ(GSTT), Ƭ(GSTZ), σ(GSTS), o(GSTO) and k(GSTK), each of which contains one or more of the homodimeric or heterodimeric isoforms.^{15, 22, 23, 24}

Tissue and organ localization: GSTs are widely expressed in mammalian tissues with a broad substrate specificity. ³ Many of the cytosolic Phase  I  and  phase  II  biotransformation  GST enzymes  are characterized   by   zone-specific  expression   in   the   liver  and the pancreas validate their role in detoxification. ^{25, 26} GST are active in normal breast tissue to protect against damage caused by reactive metabolites of chemicals, such as estrogen semiquinone and estrogen 3,4-quinone. ²⁷

GSTM1 activity: GSTM1 encodes for a class mu GST isoenzyme involved in polycyclic aromatic hydrocarbons (PAHs) detoxification. The substrates of GSTM1 include benzo (a) pyrene, benzo (c) phenanthrene, benzo (g) chrysene and other carcinogens. ^{28, 29} They can catalyze in-vitro GSH conjugation with several potent carcinogenic epoxides including aflatoxin B₁-8, 9-epoxide and electrophilic metabolites of PAHs present in tobacco smoke. ^{30, 31} Members of mu and alpha GST superfamilies possess selenium-independent GSH peroxidase activity toward organic hydroperoxides for that Cumene hydroperoxide (CuOOH) is used as substrate suggesting that these enzymes may play a role in protection against highly reactive products of oxygen metabolism including those induced by asbestos.³²

Glutathione peroxidase prevents intracellular macromolecules from free radicals during oxidative stress and its potential in vivo substrates are the hydroperoxides of phospholipids, fatty acids and DNA. ^{1, 15, 21, 32, 33, 34, 35, 36} Class alpha, mu and pi GST can detoxify harmful bulky aryl halides, ß unsaturated carbonyls including acrolein which is present in cigarette smoke ¹⁵, 4-hydroxynonenal which is produced by lipid peroxidation ^{37, 38}, adenine and thymine propenals that are generated by oxidative damage to DNA ³⁴, and aminochrome, dopachrome and noradrenochrome the quinine containing oxidation products of catecholamines. ³⁹

GSTT1 activity: Glutathione S-transferase theta (θ) is considered the most ancient of the GSTs. ²³ The encoded GSTT1 human subunit is about 25,300 Da and the gene is 8.1 kb long. ^{40, 41} GSTT1 enzymes show lower glutathione binding activity, with increased catalytic efficiency as compared with other GSTs. ^{42, 43} However, GSTT1-catalyzed reactions can also increase the toxicity of some important small dihaloalkanes such as dichloromethane. ²³ GSTT1 also catalyzes the detoxification of oxidized lipids and DNA. ^{43, 44} Halogenated organic compounds, for example, the ethylene dibromide, p-nitrobenzyl chloride, p-nitrophenethyl bromide, methyl chloride, and methyl iodide are known substrates for GSTT1. ^{45, 46, 47, 48} Class Theta GSTT1-1 is involved in GSH-dependent activation of dibromoethane (DBE). In particular, GSTT1-1 can activate dichloromethane (DCM) by conjugation with GSH to form a reactive S-chloromethylglutathione. ⁴⁹ DCM is an important compound widely used as a paint stripper, and in the synthesis of plastics and pharmaceutical drugs.

TABLE 1: CLASSIFICATION AND ORGAN LOCALIZATION OF GLUTATHIONE S-TRANSFERASES

Evolution: Significant homology between a class theta GST and a dichloromethane dehalogenase enzyme from the prokaryote Methylobacterium is suggestive of the fact that ancestral progenitor for mammalian GSTs probably arose from the theta class. ⁵⁰ Membrane-bound GST enzymes represent examples of convergent, rather than divergent, evolution. ⁵¹

CONCLUSION: Research on glutathione S-transferase family of enzymes possesses a huge scope in clinical genetics due to their association with many of the incurable life threatening diseases. There classification and organ localization through expression studies has given a way for more specific investigation. Molecular genetics with advanced DNA sequencing techniques have added a strong knowledge to their physiological network at molecular level.

More research equipped with advanced tools is required to be performed at populations and at individual level in order to provide a deep insight for personalized medicines.

CONFLICT OF INTEREST: Author declares no conflict of interest.

ACKNOWLEDGEMENT: I am grateful to Dr. Rakshit Ameta, Department of Chemistry, College of Basic and Applied Sciences, PAHER University Udaipur for his valuable suggestions to perform this review.

REFERENCES:

1. Ketterer B, and Christodoulides LG: Enzymology of cytosolic glutathione S-transferases. Advances in pharmacology, 1994; 27: 37-69.
2. Seidegard J, Vorachek WR, Pero RW, et al.: Hereditary differences in the expression of the human glutathione transferase active on trans-stilbene oxide are due to a gene deletion. Proceedings of the National Academy of Sciences of the United States of America, 1988; 85:7293–7297.
3. Hayes JD and Strange RC: Glutathione S-Transferase Polymorphisms and Their Biological Consequences. Pharmacology, 2000;61:154–166
4. Hayes JD, Pulford DJ: The glutathione S-transferase supergene family: regulation of GST and the contribution of the isoenzymes to cancer chemoprotection and drug resistance. Critical Reviews in Biochemistry and Molecular Biology, 1995; 30, 445–600.
5. Sheehan D, Meade G, Foley VM and Dowd, CA: Structure, function and evolution of glutathione transferases: Implications for classification of non-mammalian members of an ancient enzyme super family’. Biochemical Journal, 2001; 360, 1–16.
6. Mannervik B: The isozymes of glutathione transferase. Advances in Enzymology and Related Areas Molecular Biology, 1985; 57:357-417.
7. Booth J, Boyland E, Sims P: An enzyme from rat liver catalyzing conjugations with glutathione. Biochem Journal, 1961; 79:516–524.
8. Coombes B, Stakelum GS: A liver enzyme that conjugates sulfobromophthalein with glutathione. Journal Clinical Investigation, 1961; 40:981–988.
9. Prochaska HJ, Santamaria AB, Talalay P. Rapid detection of inducers of enzymes that protect against carcinogens. Proceedings of the National Academy of Sciences of the United States of America, 1992; 89:2394-2398.
10. Lin HJ, Probst-Hensch NM, Louie AD, et al: Glutathione transferase null genotype, broccoli, and lower prevalence of colorectal adenomas. Cancer Epidemiol Biomarkers Prev 1998; 7:647-652.
11. Zhang Y, Kolm RH, Mannervik B, et al: Reversible conjugation of isothiocyanates with glutathione catalyzed by human glutathione transferases. Biochemical and Biophysical Research Communications, 1995; 206:748–755.
12. London SJ, Yuan JM, Chung FL, et al: Isothiocyanates, glutathione S-transferase M1 and T1 polymorphisms, and lung cancer risk: a prospective study of men in Shanghai, China. Lancet, 2000; 356:724–729.
13. Weber BL and Nathanson KL: Low penetrance genes associated with increased risk for breast cancer. European Journal of Cancer, 2000; 36: 1193-1199.
14. Rushmore TH, and Pickett CB: Journal of Biological Chemistry, 1993 268, 11475–11478.
15. Hayes JD, McLellan LI: Glutathione and glutathione-dependent enzymes represent a coordinately regulated defense against oxidative stress. Free Radical Research, 1999; 31:273–300.
16. Hayes JD, and Strange RC: Invited commentary: potential contribution of the glutathione S-transferase supergene family to resistance to oxidative stress. Free Radical Research, 1995; 22: 193-207.
17. Mannervik B, Wildersten M: Human glutathione transferases: classification, tissue distribution, structure, and functional properties; in Pacifici GM, Fracchia GN (eds): Advances in Drug Metabolism in Man. European Commission, 1995; 407–459.
18. Whalen R, Boyer TD: Human glutathione S-transferases. Seminars in Liver Diseases 1998; 18:345– 358.
19. Ladner JE, Parsons JF, Rife CL, et al.: Parallel evolutionary pathways for glutathione transferases: structure and mechanism of the mitochondrial class Kappa enzyme rGSTK1-1. Biochemistry, 2004; 43:352-361.
20. Robinson A, Huttley GA, Booth HS, et al.: Modelling and bioinformatics studies of the human Kappa class glutathione transferase predict a novel third transferase family with homology to prokaryotic 2-hydroxychromene-2-carboxylate isomerases. Biochemistry Journal, 2004; 379:541-552.
21. Jakobsson P-J, Morgenstern R, Mancini J, et al.: Common structural features of MAPEGa widespread superfamily of membrane associated proteins with highly divergent functions in eicosanoid and glutathione metabolism. Protein Science, 1999; 8:689-692.
22. To-Figueras J, Gene M, Gomez-Catalan J, et al.: Glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) polymorphisms and lung cancer risk among Northwestern Mediterraneans. Carcinogenesis, 1997; 18 (8), 1529–1533.
23. Landi S: Mammalian class theta GST and differential susceptibility to carcinogens: a review. Mutation Research, 2000; 463: 247-283.
24. Takahiko K, Yuko Y, Mayumi T et al.: Genetic polymorphisms of human cytosol glutathione S-transferases and prostate cancer. Pharmacogenomics, 2008; 9, 93–104.
25. Oinonen T, and Lindros KO: Hormonal regulation of the zonated expression of cytochrome P-450 3A in rat Biochemistry Journal, 1995; 309, 17-35.
26. Standop J, Schneider MB, Ulrich A, Chauhan S, Moniaux N, Buchler MW, Batra SK, Pour PM. The pattern of xenobiotic-metabolizing enzymes in the human pancreas. Journal of Toxicology and Environmental Health Sciences, 2002, 65(19):1379-1400.
27. Yager JD, and Davidson NE: Estrogen carcinogenesis in breast Cancer. New England Journal Medicine, 2006;354, 270–282
28. Seidegard J, Guthenberg C, Pero RW, et al.: The trans-stilbene oxide-active glutathione transferase in human mononuclear leukocytes is identical with the hepatic glutathione transferase mu. Biochemistry Journal, 1987; 246: 783-785.
29. Hu X, Xia H, Srivastava SK, et al.: Catalytic efficiencies of allelic variants of human glutathione Stransferase P1-1 toward carcinogenic anti-diol epoxides of benzo[c]phenanthrene and benzo[g]chrysene. Cancer Research, 1998; 58:5340– 5343.
30. Johnson WW, Ueng Y-F, Widersten M et al.: Conjugation of highly reactive aflatoxin B₁ exo-8, 9-epoxide catalysed by rat and human glutathione transferases: Estimation of kinetic parameters. Biochemistry 1997; 36:3056–3060.
31. Ketterer B, Harris JM, Talaska G, et al.: The human glutathione S-transferase supergene family, its polymorphism, and its effects on susceptibility to lung cancer. Environmental Health Perspective, 1992; 98: 87-94.
32. Comstock KE, Widersten M, Hao X-Y et al.: A comparison of the enzymatic and physicochcmical properties of human glutathione transferase M4-4 and three other human mu class enzymes. Archives of Biochemistry and Biophysics, 1994; 311: 487-495.
33. Hussey A, and Hayes JD: Human mu-class glutathione S-transferases present in liver, skeletal muscle and tcsticular tissue. Biochimica et Biophysica Acta, 1993; 1203: 131-141.
34. Berhane K, Widersten M, Engstram A, et al.: Detoxication of base propenals and other alpha, beta-unsaturated aldehyde products of radical reactions and lipid peroxidation by human glutathione transferases. Proceedings of the National Academy of Sciences of the United States of America, 1994; 91: 1480-1484.
35. Mossman BT, and Marsh JP: Evidence supporting a role for active oxygen species in asbestos-induced toxicity and lung disease. Environmental Health Perspective, 1989; 81: 91-94.
36. Weitzman SA, and Gordon LI: Inflammation and cancer: role of phagocyte generated oxidants in carcinogenesis. Blood, 1990; 76: 655-663.
37. Hubatsch I, Ridderström M, Mannervik B: Human glutathione transferase A4-4: An Alpha class enzyme with high catalytic efficiency in the conjugation of 4-hydroxynonenal and other genotoxic products of lipid peroxidation. Biochemistry Journal, 1998; 330:175–179.
38. Board PG: Identification of cDNAs encoding two human Alpha class glutathione transferases (GSTA3 and GSTA4) and the heterologous expression of GSTA4-4. Biochemistry Journal, 1998; 330:827–831.

39. Baez S, Segura-Aguilar J, Widersten M, et al.: Glutathione transferases catalyse the detoxication of oxidized metabolites (o-quinones) of catecholamines and may serve as an antioxidant system preventing degenerative cellular processes. Biochemistry Journal, 1997; 324:25–28.
40. Juronen E, Tasa G, Uuskula M, et al.: Purification, characterization and tissue distribution of human class theta glutathione S-transferase T1-1. International Journal of Biochemistry and Molecular Biology, 1996; 39:21–29.
41. Coggan M, Whitbread L, Whittngton A et al.: Structure and organization of the human theta-class glutathione S-transferase and D-dopachrome tautomerase gene Biochemistry Journal, 1998; 334:617-623
42. Meyer DJ: Significance of an unusually low Km for glutathione in glutathione transferases of the alpha, mu and pi classes. Xenobiotica, 1993; 23:823–34.
43. Jemth P, Mannervik B: Kinetic characterization of recombinant human glutathione transferase T1-1, a polymorphic detoxication enzyme. Achieves of Biochemistry and Biophysics, 1997; 348: 247–54.
44. Bao Y, Jemth P, Mannervik B, et al.: Reduction of thymine hydroperoxide by phospholipids hydroperoxide glutathione peroxidase and glutathione transferases. FEBS Lett 1997; 410:210–12.
45. Whittington A, Vichai V, Webb G, et al.: Gene structure, expression and chromosomal localization of murine theta class glutathione transferase mGSTT1-1. Biochemistry Journal, 1999; 337:141–151.
46. Meyer DJ, Coles B, Pemble SE, et al.: Theta, a new class of glutathione transferases purified from rat and man. Biochemistry Journal, 1991; 274:409–414.
47. Chamberlain MP, Lock EA, Gaskell BA, et al.: The role of glutathione S-transferase- and cytochrome P450-dependent metabolism in the olfactory toxicity of methyl iodide in the rat. Achieves of Toxicology, 1998; 72:420–428.
48. DeMarini DM, Shelton ML, Warren SH, et al.: Glutathione S-transferase-mediated induction of GC/AT transitions by halomethanes in Salmonella. Environmental and Molecular Mutagenesis, 1997; 30:440–447.
49. Sherratt PJ, Pulford DJ, Harrison DJ, et al: Evidence that human class Theta glutathione S-transferase T1-1 can catalyse the activation of dichloromethane, a liver and lung carcinogen in the mouse. Comparison of the tissue distribution of GSTT1-1 with that of classes Alpha, Mu and Pi GST in human. Biochemisrty Journal, 1997; 326:837–846.
50. La Roche SD and Leisinger T: Sequence analysis and expression of the bacterial dichloromethane dehalogenase structural gene, a member of the glutathione S-transferase gene superfamily. Journal of Bacteriology, 1990; 172:164–171.
51. Nebert DW and Vasiliou V: Analysis of the glutathione S -transferase (GST) gene family. Human Genomics, 2000; 1(6): 460–464.
    

    ---

    How to cite this article:

    Suthar PC: Glutathione S-transferases: a brief on classification and GSTM1-T1 activity. Int J Pharm Sci Res 2017; 8(3): 1023-27.doi: 10.13040/IJPSR.0975-8232.8(3).1023-27.

    ---

    All © 2013 are reserved by International Journal of Pharmaceutical Sciences and Research. This Journal licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

    ---