| Abstract: | Distribution of the activities of some mitochondrial enzymes after sucrose density gradient ultracentrifugation of cell homogenates of S. cerevisiae in the early and late exponential growth phases is studied. It is demonstrated that young yeast cells have a characteristic complex distribution of NADH oxidase (cyanide-sensitive), succinate:ferricyanide-oxidoreductase (or succinate:2,6-dichlorophenol indophenol-oxidoreductase), NADH:2,6-dichlorophenol indophenol-oxidoreductase and cytochrome oxidase activities in sucrose density gradient; the distribution patterns of these activities are different. All the above activities are detected in a single relatively narrow band in mature yeast cells. Similar results are obtained in the experiments with glucose or galactose as a carbon source in the yeast growth media. The Arrhenius plots for NADH oxidase (as well as for succinate:2,6-dichlorophenol indophenol-oxidoreductase) activity do not differ in the case of "light" and "heavy" mitochondrial structures characteristic of yeast cells in the early exponential growth phase. Nevertheless, "light" and "heavy" mitochondrial structures differ with respect of the arrangement of certain respiratory chain components in their membranes NADH-dehydrogenase and cytochrome oxidase). This conclusion is drawn from the results obtained in the study of the interaction of the two types of structures with Fe(CN)6(3-), a non-penetrating ion and the antiserum to yeast mitochondria. |
