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|
Expected Taxonomic Range:
glutathione amide (GASH) is one of several glutathione-related compounds that are found in prokaryotes [Fahey01]. The compound is produced at milimolar levels by the purple photosynthetic bacteria Allochromatium vinosum and Marichromatium gracile [Bartsch96].
A GASH-dependent peroxidase has been identified in Marichromatium gracile. The enzyme belongs to the peroxiredoxin family, even though other members of the family are thioredoxin-dependent. Since this enzyme is capable of reducing hydrogen peroxide, and since Marichromatium gracile, while an anaerobic organism, is capable of surviving under microaerobic conditions, it was suggested that glutathione amide mediated peroxide detoxification represents an early adaptation for fighting oxidative stress [Vergauwen01].
During the reduction of peroxide, GASH forms a disulfide, similar to glutathione disulfide. However, GASH is maintained in a reduced state by a dedicated glutathione amide reductase (GAR), which converts it back to the reduced form, utilizing NADH [Vergauwen01].
When grown on hydrogen sulfide as a hydrogen donor, most of the GASH is converted to a perthiol form (GASSH), suggesting that it may be involved in sulfide metabolism in the organism, perhaps assiting the import of sufide into the cell, where it forms sulfur globules [Pott98, Bartsch96].
Another amide derivative of glutathione is glutathionylspermidine (see glutathionylspermidine biosynthesis).
Pott98: Pott AS, Dahl C (1998). "Sirohaem sulfite reductase and other proteins encoded by genes at the dsr locus of Chromatium vinosum are involved in the oxidation of intracellular sulfur." Microbiology 144 ( Pt 7);1881-94. PMID: 9695921
Vergauwen01: Vergauwen B, Pauwels F, Jacquemotte F, Meyer TE, Cusanovich MA, Bartsch RG, Van Beeumen JJ (2001). "Characterization of glutathione amide reductase from Chromatium gracile. Identification of a novel thiol peroxidase (Prx/Grx) fueled by glutathione amide redox cycling." J Biol Chem 276(24);20890-7. PMID: 11399772
Vergauwen02: Vergauwen B, Van Petegem F, Remaut H, Pauwels F, Van Beeumen JJ (2002). "Crystallization and preliminary X-ray crystallographic analysis of glutathione amide reductase from Chromatium gracile." Acta Crystallogr D Biol Crystallogr 58(Pt 2);339-40. PMID: 11807270
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