Abstract
Plasma membrane (PM) vesicles isolated from the yeast Saccharomyces cerevisiae (wild-type NCIM 3078, and a MG 21290 mutant pma 1-1) were used to monitor the effect of the detergents, 3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate (Chaps) and Triton X-100, on H+-ATPase (E.C. 3.6.1.35), NADH oxidase and NADH- hexacynoferrate (III)[HCF (III)] oxidoreductase (E.C. 1.6.99.3) activities. The results obtained show that Triton X-100 inhibited both membrane bound and solubilized NADH-dependent redox activities. The nature of this inhibition as determined for NADH–HCF(III) oxidoreductase was non-competitive and the Ki values for wild and mutant enzymes were 1.2 × 10−5 M and 8.0 × 10−6 M, respectively. The findings are interpreted, in view of the established reports, that the active site architecture of PM bound NADH-dependent oxidoreductase in yeast is likely to be different than in other eukaryotes.