| Popis: |
1. A procedure for the preparation of protoplasts from yeast Saccharomyces cerevisiae harvested in their stationary phase of growth on glucose was modified and mitochondria were isolated from the protoplasts. 2. Oxidative activity, phosphorylation efficiency and sensitivity to 2,4-dinitrophenol and oligomycin of these mitochondria were similar as previously reported for mitochondria from lactate-grown Saccharomyces carlsbergensis. 3. The mitochondria exhibited a Mg2+-dependent ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity with two pH optima, one at pH 6.2 and another at 9.5. Properties of the ATPase at the two pH optima with respect to activation by dinitrophenol, requirement for cations, stimulation by detergents, as well as dependence on ATP and Mg2+ concentrations, were studied. The activity at pH 9.5 was strongly inhibited by oligomycin and azide and only moderately by fluoride. Inverse sensitivity towards the three inhibitors was observed at pH 6.2. 4. The mitochondria catalyzed ATP-inorganic phosphate exchange reaction which was inhibited by dinitrophenol, azide and oligomycin. |
