MetaCyc Pathway: glutathione biosynthesis
Inferred from experimentTraceable author statement to experimental support

Enzyme View:

Pathway diagram: glutathione biosynthesis

This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Superclasses: BiosynthesisCofactors, Prosthetic Groups, Electron Carriers BiosynthesisReductants Biosynthesis

Some taxa known to possess this pathway include : Arabidopsis thaliana colInferred from experiment [Xiang01], Brassica juncea, Escherichia coli K-12 substr. MG1655, Populus tremula x Populus alba

Expected Taxonomic Range: Bacteria , Eukaryota

General Background

Thiols are compounds that play a major role in the detoxification of stress-inducing factors. In mammals, the major thiol is the tripeptide glutathione (γ-Glu-Cys-Gly, known as GSH). Toxins are conjugated to GSH in the liver by a dedicated enzyme, resulting in a cysteine-toxin conjugate. The conjugate is acetylated in the kidney to form mercapturate, and is then excreted [Hinchman94] (see glutathione-mediated detoxification I). In addition to oxidative stress management, low molecular weight thiols have been found to be involved in critical cellular processes including DNA synthesis and formaldehyde reduction [Patel98].

Pathogenic bacteria live in a particularly hostile environment, in which the host deliberately generates toxins, including reactive oxygen species, to destroy the invading organism. Thus thiols are particularly important for the survival of these organisms. While GSH is the major thiol in eukaryotic organisms, Gram negative bacteria and the majority of Gram positive bacteria, it is not universal. In some organisms other thiols have taken its role, including coenzyme M, trypanothione, ergothioneine, mycothiol and the ovothiols.

About This Pathway

The synthesis of GSH from its three amino acid precursors L-glutamate, L-cysteine and glycine takes place in the cytosol. GSH is synthesized in all mammalian cells, many plants, and most Gram negative bacteria. In mammals, the liver is a major site of biosynthesis.

GSH is synthesized in a two-step reaction, catalyzed by γ-glutamate-cysteine ligase and by glutathione synthetase, requiring a total of two moles of ATP per mole of GSH. This ATP-dependent coupling of amino acid monomers and elongating peptides by soluble enzymes is very unusual, as oligopeptides are usually formed either by ribosomes or by nonribosomal peptide synthases. A similar mechanism is also found in the formation of the bacterial cell wall pentapeptide.

The first step in glutathione biosynthesis is controlled by negative feedback from its end product, GSH. However, feedback inhibition can be partially prevented by an excess of glutamate that blocks the regulatory site on the enzyme [Meister84, Meister83]. When GSH is consumed and feedback inhibition is lost, the availability of cysteine as a precursor can become the limiting factor [Wang98].

In plants

Glutathione is an antioxidant that counteracts reactive oxygen species thus reducing oxidative stress [Noctor98]. It is recognized as a major player in detoxifying xenobiotics [Matringe88] by forming less reactive or storage conjugates catalyzed by GHS S-transferases [Marrs96]. Glutathione has also been reported to detoxify air pollutants such as ozone and sulfur dioxide [Madamanchi91].

GHS is discussed as important storage form of reduced sulfur regulating inter-organ sulfur allocation and its biosynthesis seems to be coupled with the sulfate assimilation pathway (see sulfate reduction II (assimilatory)) [Meyer02]. As a precursor for phytochelatin, the principal metal-binding agent in plants, glutathione is considered a vital component for the detoxification of heavy metals [Grill] [Grill89, Xiang01].

The biosynthesis of glutathione is universally catalyzed in all organisms by two enzymes, glutamate-cysteine ligase [May94] [Jez04a] regarded as the rate-limiting step of the pathway [Richman75] and glutathione synthetase [Ullmann96] [Wang96] [Jez04].

The regulation of the plant enzymes is unlike those reported from other eucaryotes. For the glutamate-cysteine ligase a conformational change has been observed as means to modify enzyme activities in response to redox conditions. That differs from mammalian enzymes that regulate activity through a regulatory subunit of the enzyme [Jez04a].

Superpathways: γ-glutamyl cycle


Created 31-Jan-1995 by Riley M, Marine Biological Laboratory
Reviewed 08-Nov-2006 by Foerster H, TAIR
Last-Curated 16-Dec-2009 by Keseler I, SRI International


Grill: Grill E, Winnacker E-L, Zenk MH "Phytochelatins: The Principal Heavy-Metal Complexing Peptides of Higher Plants." Science, 230(4726), 674 - 676.

Grill89: Grill E, Loffler S, Winnacker EL, Zenk MH (1989). "Phytochelatins, the heavy-metal-binding peptides of plants, are synthesized from glutathione by a specific gamma-glutamylcysteine dipeptidyl transpeptidase (phytochelatin synthase)." Proc Natl Acad Sci U S A 86(18);6838-6842. PMID: 16594069

Hinchman94: Hinchman CA, Ballatori N (1994). "Glutathione conjugation and conversion to mercapturic acids can occur as an intrahepatic process." J Toxicol Environ Health 41(4);387-409. PMID: 8145281

Jez04: Jez JM, Cahoon RE (2004). "Kinetic mechanism of glutathione synthetase from Arabidopsis thaliana." J Biol Chem 279(41);42726-31. PMID: 15302873

Jez04a: Jez JM, Cahoon RE, Chen S (2004). "Arabidopsis thaliana glutamate-cysteine ligase: functional properties, kinetic mechanism, and regulation of activity." J Biol Chem 279(32);33463-70. PMID: 15180996

Madamanchi91: Madamanchi NR, Alscher RG (1991). "Metabolic Bases for Differences in Sensitivity of Two Pea Cultivars to Sulfur Dioxide." Plant Physiol 97(1);88-93. PMID: 16668420

Marrs96: Marrs KA (1996). "The functions and regulation of glutathione S-transferases in plants." Annu Rev Plant Physiol Plant Mol Biol 47;127-158. PMID: 15012285

Matringe88: Matringe M, Scalla R (1988). "Studies on the Mode of Action of Acifluorfen-Methyl in Nonchlorophyllous Soybean Cells : Accumulation of Tetrapyrroles." Plant Physiol 86(2);619-622. PMID: 16665956

May94: May MJ, Leaver CL (1994). "Arabidopsis thaliana γ-glutamylcysteine synthetase is structurally unrelated to mammalian, yeast, and Escherichia coli homologs." Proc. Natl. Acad. Sci. USA, 91, 10059-10063.

Meister83: Meister A, Anderson ME (1983). "Glutathione." Annu Rev Biochem 52;711-60. PMID: 6137189

Meister84: Meister A (1984). "New aspects of glutathione biochemistry and transport--selective alteration of glutathione metabolism." Nutr Rev 42(12);397-410. PMID: 6151157

Meyer02: Meyer AJ, Fricker MD (2002). "Control of demand-driven biosynthesis of glutathione in green Arabidopsis suspension culture cells." Plant Physiol 130(4);1927-37. PMID: 12481075

Noctor98: Noctor G, Arisi A-CM, Jouanin L, Kunert KJ, Rennenberg H, Foyer CH (1998). "Glutathione: biosynthesis, metabolism and relationship to stress tolerance explored in transformed plants." Journal of Experimental Botany, 49(321), 623-647.

Patel98: Patel, M. P., Blanchard, J. S. (1998). "Synthesis of Des-myo-Inositol Mycothiol and Demonstration of a Mycobacterial Specific Reductase Activity." J. Am. Chem. Soc. 120:11538-11539.

Richman75: Richman PG, Meister A (1975). "Regulation of γ-glutamyl-cysteine synthetase by nonallosteric feedback inhibition by glutathione." J Biol Chem 250(4);1422-6. PMID: 1112810

Ullmann96: Ullmann P, Gondet L, Potier S, Bach TJ (1996). "Cloning of Arabidopsis thaliana glutathione synthetase (GSH2) by functional complementation of a yeast gsh2 mutant." Eur J Biochem 236(2);662-9. PMID: 8612643

Wang96: Wang CL, Oliver DJ (1996). "Cloning of the cDNA and genomic clones for glutathione synthetase from Arabidopsis thaliana and complementation of a gsh2 mutant in fission yeast." Plant Mol Biol 31(6);1093-104. PMID: 8914526

Wang98: Wang W, Ballatori N (1998). "Endogenous glutathione conjugates: occurrence and biological functions." Pharmacol Rev 50(3);335-56. PMID: 9755286

Xiang01: Xiang C, Werner BL, Christensen EM, Oliver DJ (2001). "The biological functions of glutathione revisited in arabidopsis transgenic plants with altered glutathione levels." Plant Physiol 126(2);564-74. PMID: 11402187

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Apontoweil75: Apontoweil P, Berends W (1975). "Glutathione biosynthesis in Escherichia coli K 12. Properties of the enzymes and regulation." Biochim Biophys Acta 1975;399(1);1-9. PMID: 238647

Apontoweil75a: Apontoweil P, Berends W (1975). "Isolation and initial characterization of glutathione-deficient mutants of Escherichia coli K 12." Biochim Biophys Acta 399(1);10-22. PMID: 1096956

BRENDA14: BRENDA team (2014). Imported from BRENDA version existing on Aug 2014.

Daws89: Daws T, Lim CJ, Fuchs JA (1989). "In vitro construction of gshB::kan in Escherichia coli and use of gshB::kan in mapping the gshB locus." J Bacteriol 171(9);5218-21. PMID: 2670910

DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114

Fan95: Fan C, Moews PC, Shi Y, Walsh CT, Knox JR (1995). "A common fold for peptide synthetases cleaving ATP to ADP: glutathione synthetase and D-alanine:d-alanine ligase of Escherichia coli." Proc Natl Acad Sci U S A 92(4);1172-6. PMID: 7862655

Faulkner08: Faulkner MJ, Veeravalli K, Gon S, Georgiou G, Beckwith J (2008). "Functional plasticity of a peroxidase allows evolution of diverse disulfide-reducing pathways." Proc Natl Acad Sci U S A 105(18);6735-40. PMID: 18456836

Fuchs75: Fuchs JA, Warner HR (1975). "Isolation of an Escherichia coli mutant deficient in glutathione synthesis." J Bacteriol 124(1);140-8. PMID: 1100598

Gali95: Gali RR, Board PG (1995). "Sequencing and expression of a cDNA for human glutathione synthetase." Biochem J 310 ( Pt 1);353-8. PMID: 7646467

GOA01: GOA, MGI (2001). "Gene Ontology annotation based on Enzyme Commission mapping." Genomics 74;121-128.

GOA01a: GOA, DDB, FB, MGI, ZFIN (2001). "Gene Ontology annotation through association of InterPro records with GO terms."

GOA06: GOA, SIB (2006). "Electronic Gene Ontology annotations created by transferring manual GO annotations between orthologous microbial proteins."

Greenberg86: Greenberg JT, Demple B (1986). "Glutathione in Escherichia coli is dispensable for resistance to H2O2 and gamma radiation." J Bacteriol 168(2);1026-9. PMID: 3536846

Gushima83: Gushima H, Miya T, Murata K, Kimura A (1983). "Purification and characterization of glutathione synthetase from Escherichia coli B." J Appl Biochem 1983;5(3);210-8. PMID: 6389479

Hara95: Hara T, Tanaka T, Kato H, Nishioka T, Oda J (1995). "Site-directed mutagenesis of glutathione synthetase from Escherichia coli B: mapping of the gamma-L-glutamyl-L-cysteine-binding site." Protein Eng 8(7);711-6. PMID: 8577699

Hara96: Hara T, Kato H, Katsube Y, Oda J (1996). "A pseudo-michaelis quaternary complex in the reverse reaction of a ligase: structure of Escherichia coli B glutathione synthetase complexed with ADP, glutathione, and sulfate at 2.0 A resolution." Biochemistry 35(37);11967-74. PMID: 8810901

Harrison09: Harrison JJ, Tremaroli V, Stan MA, Chan CS, Vacchi-Suzzi C, Heyne BJ, Parsek MR, Ceri H, Turner RJ (2009). "Chromosomal antioxidant genes have metal ion-specific roles as determinants of bacterial metal tolerance." Environ Microbiol 11(10);2491-509. PMID: 19555372

Harth05: Harth G, Maslesa-Galic S, Tullius MV, Horwitz MA (2005). "All four Mycobacterium tuberculosis glnA genes encode glutamine synthetase activities but only GlnA1 is abundantly expressed and essential for bacterial homeostasis." Mol Microbiol 58(4);1157-72. PMID: 16262797

Helbig08: Helbig K, Bleuel C, Krauss GJ, Nies DH (2008). "Glutathione and transition-metal homeostasis in Escherichia coli." J Bacteriol 190(15);5431-8. PMID: 18539744

Helbig08a: Helbig K, Grosse C, Nies DH (2008). "Cadmium toxicity in glutathione mutants of Escherichia coli." J Bacteriol 190(15);5439-54. PMID: 18539742

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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