Identification and characteristics of a novel mitochondrial ATPase in rat liver.

A novel ATPase is postulated for isolated mitochondria and mitoblasts of rat liver. The enzyme is active in the presence of oligomycin and carboxyatractyloside. It can be distinguished from other well-known mitochondrial and non-mitochondrial ATPases by its insensitivity to common ATPase inhibitors and effectors and by digitonin treatment. The ATPase is localized on the outer side of the inner mitochondrial membrane. It is activated by Mg2+ in the alkaline pH range and exhibits a biphasic kinetics. The novel external ATPase of rat liver mitochondria possesses similar properties with respect to ATP-dependent protease.