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:||Biosynthesis → Cofactors, Prosthetic Groups, Electron Carriers Biosynthesis → Reductants Biosynthesis|
Thiols such as glutathione play several major roles in the cell, including maintainance of the redox balance, fighting reactive oxygen and nitrogen species, and the detoxification of many other toxins and stress-inducing factors (see glutathione-mediated detoxification I). In most organisms the major thiol is the tripeptide glutathione (γ-Glu-Cys-Gly, known as GSH), whose intracellular concentration ranges from 0.5-10 mM (see γ-glutamyl cycle).
Most of the glutathione pool is kept in its reduced form. For example, in Escherichia coli, the ratio of reduced to oxidized glutathione is 200:1 [Ritz01]. The functionality of GSH largely depends on its being in a reduced form.
About This Pathway
One of the main roles of glutathione in the cell is the reduction of other molecules, such as peroxides or protein-disulfide groups. In this pathway the process is represnted by EC 18.104.22.168, phospholipid-hydroperoxide glutathione peroxidase:
In the process two molecules of GSH are condensed into a single molecule of the oxidized form, glutathione disulfide. In eukaryotes this oxidation reaction is often catalyzed by enzymes belonging to the glutathione peroxidase family. It was believed that glutathione-dependent peroxidases are not present in prokaryotic organisms, but recently some glutathione-dependent peroxidases have been discovered in bacteria [Pauwels03].
The glutathione disulfide is reduced back to GSH by the action of EC 22.214.171.124, glutathione-disulfide reductase
Another redox cycle involving glutathione is described in glutathione-glutaredoxin redox reactions.
Pauwels03: Pauwels F, Vergauwen B, Vanrobaeys F, Devreese B, Van Beeumen JJ (2003). "Purification and characterization of a chimeric enzyme from Haemophilus influenzae Rd that exhibits glutathione-dependent peroxidase activity." J Biol Chem 278(19);16658-66. PMID: 12606554
Anderson90a: Anderson, James, Hess, John, Chevone, Boris "Purification, characterization, and immunological properties of two isoforms of glutathione reductase from Eastern white pine needles." Plant Physiology, 1990, 94:1402-1409.
Arenas10: Arenas FA, Diaz WA, Leal CA, Perez-Donoso JM, Imlay JA, Vasquez CC (2010). "The Escherichia coli btuE gene, encodes a glutathione peroxidase that is induced under oxidative stress conditions." Biochem Biophys Res Commun 398(4);690-4. PMID: 20621065
Bjornstedt94: Bjornstedt M, Xue J, Huang W, Akesson B, Holmgren A (1994). "The thioredoxin and glutaredoxin systems are efficient electron donors to human plasma glutathione peroxidase." J Biol Chem 269(47);29382-4. PMID: 7961915
Chu93: Chu FF, Doroshow JH, Esworthy RS (1993). "Expression, characterization, and tissue distribution of a new cellular selenium-dependent glutathione peroxidase, GSHPx-GI." J Biol Chem 268(4);2571-6. PMID: 8428933
Esworthy94: Esworthy RS, Doan K, Doroshow JH, Chu FF (1994). "Cloning and sequencing of the cDNA encoding a human testis phospholipid hydroperoxide glutathione peroxidase." Gene 144(2);317-8. PMID: 8039723
Henderson91: Henderson GB, Murgolo NJ, Kuriyan J, Osapay K, Kominos D, Berry A, Scrutton NS, Hinchliffe NW, Perham RN, Cerami A (1991). "Engineering the substrate specificity of glutathione reductase toward that of trypanothione reduction." Proc Natl Acad Sci U S A 88(19);8769-73. PMID: 1924337
KrohneEhrich77: Krohne-Ehrich G, Schirmer RH, Untucht-Grau R (1977). "Glutathione reductase from human erythrocytes. Isolation of the enzyme and sequence analysis of the redox-active peptide." Eur J Biochem 80(1);65-71. PMID: 923580
Mata84: Mata AM, Pinto MC, Lopez-Barea J (1984). "Purification by affinity chromatography of glutathione reductase (EC 126.96.36.199) from Escherichia coli and characterization of such enzyme." Z Naturforsch [C] 39(9-10);908-15. PMID: 6393625
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