Glutathione system activity

G. Benzi and A. Moretti, Age- and peroxidative stress-related modifications of the cerebral enzymatic activities linked to mitochondria and the glutathione system. Free Radical Biol. Med. 19, 77-101 (1995). 

Fukami, J., and Shishido, T., Nature of a soluble glutathione-dependent enzyme system active in cleavage of methyl parathion to desmethyl parathion, J. Econ. Entomol., 59, 1338-1346, 1966. 

We know that phosphorylation of eIP-2 occurs in lysates incubated with oxidised glutathione (26, 57) > an > the reasons discussed previously, it probably also occurs in all the other inhibitory conditions. Although the kinase systems activated by haem-deficiency and by dsRNA seem to be separate entities, it seems inherently improbable that each of the other inhibitory conditions operates through a separate kinase system. It is more likely that some of the kinase systems can be activated in more than one way, and our preliminary experiments suggest that the inhibition caused by hi hydrostatic pressure and by high temperature is due to an entity which so closely resembles the reversible form of the haem-controlled repressor that it must surely be the same. 

Furthermore, the redox system of the cell could be influenced by the cobalt cluster. Compound 31 has been shown to form disulfides when treated with thiols such as glutathione or cysteine [124]. The activity of glutathione reductase is a very sensitive indicator for the redox state within cells. It has been shown that glutathione reductase activity was not influenced by 34, 31, ASS, or the alkyne ligand of 31 [109]. A mechanism of action based on changing the redox state of the cell can therefore be excluded. 

Glutathione is active as coenzyme (E 2.1) and, together with its dimeric disulfide, is an important redox system (E 2.2). In animals it forms conjugates with different secondary products (E 1). 

All this biochemical information points to a general role of the glutathione system in the metabolic activity of both eumelanic and phaeomelanic melanocytes. Hov/ever, whether glutathione is also specifically involved in the biosynthesis of the cysteinyldopas required for phaeomelanin formation remains to be determined, and the answer obtained will unquestionably contribute to our understanding of the synthetizing activity of mammalian melanocytes. 

Disulfides. As shown in Figure 4, the and h-chains of insulin are connected by two disulfide bridges and there is an intrachain cycHc disulfide link on the -chain (see Insulin and other antidiabetic drugs). Vasopressin [9034-50-8] and oxytocin [50-56-6] also contain disulfide links (48). Oxidation of thiols to disulfides and reduction of the latter back to thiols are quite common and important in biological systems, eg, cysteine to cystine or reduced Hpoic acid to oxidized Hpoic acid. Many enzymes depend on free SH groups for activation—deactivation reactions. The oxidation—reduction of glutathione (Glu-Cys-Gly) depends on the sulfhydryl group from cysteine. 

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