ELECTRON TRANSPORT DEPENDENT ADENOSINE TRIPHOSPHATASE ACTIVITY IN CASTOR BEAN ENDOSPERM MITOCHONDRIA

The release of inorganic phosphate from ATP by mitochondria isolated from endosperms of castor bean (Ricinus communis) was stimulated by Mg++, but not by Ca++. EDTA, succinate, NADH2 or oligomycin depressed the reaction. The depression by succinate was removed by KCN, antimycin A or anoxia. DNP alone did not affect activity but did stimulate the Pi release in the presence of succinate under aerobic conditions. Enhanced Pi release in the presence of succinate and DNP was cancelled by KCN, antimycin A, oligomycin or anoxia. On the basis of these results, the mechanism of ATPase action in castor bean endosperm mitochondria is discussed. © 1969 Oxford University Press.