Specificity of lipids and coenzyme Q in mitochondrial NADH and succin-oxidase of beef heart and S. cerevisiae

The organic structural specificity of coenzyme Q in NADH- and succin-oxidase has been studied with mitochondria from the yeast, S. cerevisiae, and compared with the specificity for mitochondrial enzyme systems from beef heart. The specificity of lipids in CoQ-enzyme systems has also been studied. The origin and concentration of micellar phospholipids used as carriers for the CoQ homologs profoundly affects the restoration of NADH-oxidase in pentane-extracted mitochondria both from yeast and beef heart. High concentrations of phospholipids induce a decrease of the NADH-oxidase activity which had been restored by the lower homologs of CoQ. The activity with CoQ 1-CoQ 4 was higher than that with the natural CoQ 6 in yeast mitochondria, and was lower than that with the natural CoQ 10 in beef heart mitochondria, irrespective of the concentration of phospholipids. Mitochondrial phospholipids of yeast were more effective than soybean phospholipids in supporting restoration of NADH-oxidase by the higher homologs in pentane-extracted mitochondria of yeast. This difference was not evident for succin-oxidase from yeast and beef heart. Succin-oxidase from both sources was similarly restored by the homologs CoQ 2-Q 10 independently of the phospholipid concentration. According to these data, there are two sites for CoQ 6 in yeast mitochondria as there are two sites for CoQ 10 in beef heart mitochondria. The nature of the site in NADH-oxidase of yeast and of beef heart is different.