title: Evidence for a role of a vicinal dithiol in catalysis and proton pumping in mitochondrial nicotinamide nucleotide transhydrogenase.
abstract: The effect of glutathione, glutathione disulfide and the dithiol reagent phenylarsine oxide on purified soluble as well as reconstituted mitochondrial nicotinamide nucleotide transhydrogenase from beef heart was investigated. Glutathione disulfide and phenylarsine oxide caused an inhibition of transhydrogenase, the extent of which was dependent on the presence of either of the transhydrogenase substrates. In the absence of NADPH glutathione protected partially against inactivation by glutathione disulfide and phenylarsine oxide. In the presence of NADPH glutathione also inhibited transhydrogenase. Reconstituted transhydrogenase vesicles behaved differently as compared to the soluble transhydrogenase and was partially uncoupled by GSSG. It is concluded that transhydrogenase contains a dithiol that is essential for catalysis as well as for proton translocation.
mesh_terms: D005978:Glutathione / Q000494:pharmacology; D008928:Mitochondria / Q000201:enzymology*; D009243:NAD / Q000494:pharmacology; D009247:NADH, NADPH Oxidoreductases / Q000032:analysis*; D009249:NADP / Q000494:pharmacology; D009250:NADP Transhydrogenases / Q000032:analysis* / Q000037:antagonists & inhibitors; D011522:Protons; D013438:Sulfhydryl Compounds / Q000032:analysis*
chemical_list: D011522:Protons; D013438:Sulfhydryl Compounds; D009243:NAD; D009249:NADP; D009247:NADH, NADPH Oxidoreductases; D009250:NADP Transhydrogenases; D005978:Glutathione