Teine residues are susceptible to autoxidation, that is catalyzed by heavy metal ions complexed by the thiol, amino and carboxylate groups.40 In glutathione, the amino and carboxylate groups of cysteine are involved in amide bonds with glutamate and glycine, which SSTR2 Biological Activity substantially decreases the rate of autoxidation. The presence of higher salt decreases the price of autoxidation of Cys, so formation of amide bonds to glutamate and glycine is significantly less essential. Curiously, -Glu-Cys is really far more steady than glutathione inside the presence of high salt.12 Hence, the easier thiol serves completely effectively inside the halobacteria, and there has apparently been no selective stress to expend energy and carbon to add an added glycine residue.39 Genes encoding closely related homologs of Halobacterium sp. NRC-1 GCR are found inside the genomes of 12 on the 18 halobacteria for which full genome sequences are out there (Figure 7). Surprisingly, we couldn’t detect homologs of GCR from six halobacteria. Every single of these species includes a homolog of GshA with 60?0 identity for the Halobacterium sp. NRC-1 GshA, so presumably all are capable of producing -Glu-Cys. Halobacteria that lack a homolog of GCR might have a non-homologous enzyme that serves this function. Alternatively, these Archaea may use a various low molecular weight thiol, possibly 1 derived from -Glu-Cys. It is intriguing that there’s such diversity even within the Halobacterium clade.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptHalobacterium sp. NRC-1 GCR belongs towards the pyridine nucleotide-disulfide oxidoreductase household. This makes an incredible deal of sense, provided the capacity of all enzymes in the household to minimize a disulfide bond using electrons derived from NADPH which are passed via a flavin along with a disulfide around the enzyme ahead of reaching the substrate. What exactly is surprising will be the high RGS16 Species degree of sequence divergence amongst the loved ones members (Figure 4), which suggests that this family members has been evolving for a extremely lengthy time frame, and tends to make phylogenetic analysis difficult. Enzymes involved in synthesis of low molecular weight thiols and theBiochemistry. Author manuscript; available in PMC 2014 October 28.Kim and CopleyPagereduction of the corresponding disulfides likely evolved in the time O2 started to seem within the atmosphere39 greater than two.five billion years ago.41 Dihydrolipoamide dehydrogenase, which is a component of pyruvate dehydrogenase, -ketoglutarate dehydrogenase complicated as well as the glycine cleavage technique, was most likely present in the last universal popular ancestor42, and may have been the progenitor of the household of pyridine nucleotide disulfide reductases that now consists of glutathione reductase, trypanothione reductase, mycothione reductase, mercuric reductase and now GCR.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptSupplementary MaterialRefer to Internet version on PubMed Central for supplementary material.AcknowledgmentsFunding Source Statement: This work was supported by NIH RO1 GM083285 to SDC.AbbreviationsGCR -Glu-Cys DNA NMR NADPH NAD ESI-MS/MS SDS-PAGE AEBSF EDTA IPTG tDBDF Bis–glutamylcystine reductase -Glutamylcysteine deoxyribonucleotide nuclear magnetic resonance spectroscopy nicotinamide adenine dinucleotide phosphate nicotineamide adenine dinucleotide electrospray ionization tandem mass spectrometry sodium dodecyl sulfate polyacrylamide gel electrophoresis 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride ethylenediaminetetraacetic ac.