MgATP-induced inhibition of the enzymic activity of chloroform-released ox-heart mitochondrial ATPase

Preincubation of the chloroform-released ox-heart mitochondrial ATPase with its substrate, MgATP, results in a time-dependent inhibition of its ATPase activity. The inhibition is irreversible on the time-scale of an ATPase assay. It is not due to the accumulation of ADP and P i. The extent of the inhibition is proportional to the number of turnovers of the enzyme during the preincubation period. It is suggested that the MgATP-induced inhibition described here is due to an intermediate enzyme-substrate complex of the ATP-hydrolytic pathway becoming converted into an inhibited enzyme species.