Glutathione hydrogen transferase

The kinetics of the piperidino-defluorination reaction of l-fluoro-2,4-dinitrobenzene have been studied in non-aqueous reverse micelles consisting of ethylene glycol-AOT-/ -heptane or DMF-AOT-n-heptane. The reaction, which is not base catalysed, is accelerated when DMF, a non-hydrogen bond donor solvent, is used in the micelle core.22 Catalysis by human glutathione 5-transferase M la-la of the reaction of glutathione with 1-chloro- and l-fluoro-2,4-dinitrobenzenes has been investigated. Much stronger enzymatic catalysis was observed in the case of the dechlorination reaction than for the defluorination and a transition-state model was proposed 23... 

The glutathione S-transferases are a group of enzymes, which catalyse the nucleophiUc attack of GSH to many kinds of electrophiles (Mannervik and Danielson 1988). Most of glutathione S-transferase isoenzymes locaUze in the cytoplasm and are classified into 3 groups class o, n and n. Human glutathione S-transferase Ji can be selectively reduced by hydrogen peroxide (Tamai et al. 1990). Rat class enzymes were activated by the xanthine-xanthine oxidase system (Murata et al. 1990). 

Compounds that increase the resistance to oxidative stress were identified by their ability to increase the IC50 of the human neuronal cell line IMR-32 for hydrogen peroxide (Fiander and Schneider 1999). All of the compounds identified that increased the IC50 (238 53% by 2 pM 1-nitro-l-cyclohexene 172 51% by 2 iM 3-methylene-2-norbornanone) also increased the specific activity of glutathione S-transferase. In addition, compound-caused increases in the specific activity of glutathione S-transferase correlated with compound-caused increases in the IC50, the expected behaviour if glutathione S-transferase was a critical enzyme. 

Glutathione S-transferases are susceptible to inactivation by reactive nitrogen species. Treatment of isolated glutathione S-transferases or rat liver homogenates with either peroxynitrite, the myeloper-oxidase/hydrogen peroxide/nitrite system, or tetra-nitromethane, resulted in loss of glutathione S-transferase activity with a concomitant increase in the formation of protein-associated 3-nitrotyrosine (Wong et al. 2001). 

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