Oxidized glutathione reductase inhibition

Glutathione reductase (GR) catalyzes the reduction of oxidized glutathione (GSSG) to reduced glutathione (GSH) using NADPH provided from the hexose monophosphate pathway. GR, a ubiquitous flavoenzyme, maintains a high value of two for the GSH/GSSG ratio in the red blood cells. l,3-Bis(2-chloroethyl)-nitrosourea (BCNU) selectively inhibits cellular GR. GR is composed of two identical subunits, each of molecular mass 50 kDa (S8). The three-dimensional structure and mechanism of catalysis have been established for human GR (K17). 

The inhibition constant for the process in which the enzyme glutathione reductase is inhibited by G6P was determined by measuring the initial rate of the oxidation of NADPH at various concentrations of GSSG. This procedure was repeated four times, each time with a separate concentration of the inhibitor G6P All the solutions were prepeared in 0.1 M Tris buffer pH 8 containing 10 mM MgCl2 and 0.94 mM EDTA. 

Moreover, intracellular accumulation and cytochrome P450 catalyzed bioactivation of p-lactams such as cephaloridine overwhelms of the GSH redox cycle by inhibiting glutathione reductase activity [35, 56], depletion of GSH and accumulation of GSSG [35, 42, 49,56]. Most of GSSG formed is subsequently reduced by glutathione reductase and GSH is regenerated with concomitant oxidation (consumption) of NADPH to NADP+ [104]. 

Increased oxidative stress in the RAW 264.7 macrophage cell line is partially mediated via the S-nitrosothiol-induced inhibition of glutathione reductase (EC 1.6.4.2) (Butzer et al. 1999). Fujii et al. (2000) isolated a cDNA for rat glutathione reductase and constructed a baculovirus system to produce recombinant glutathione reductase on a large scale. NO donors (S-nitrosoglutathione, SIN-1, and S-nitroso-N-acetyl-D,L-penicillamine) inhibited the enzymatic activities of purified glutathione reductase. 

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