Polymorphism of the membrane proteinases of the mitochondria

Three protein fractions capable of catalyzing the proteolysis of cytochrome c and three other fractions catalyzing the hydrolysis of N-α-benzoyl-L-arginine-p-nitroanilide (BAPA) and N-α-benzoyl-L-arginine-β-naphthylamide (BANA) were separated by electrophoresis in polyacrylamide gel in the absence of SDS detergent extracts from ultrasonic submitochondrial particles (SMP). The indicated fractions were isolated from gel and studied according to a series of parameters. It was shown that cytochrome c hydrolases have the same molecular weight (17,000) but different isoelectric points (4.0, 4.2, and 4.4). The total cytochrome c hydrolase activity of these enzymes was inhibited by phenylmethylsulfonyl fluoride but was insensitive to ethylenediaminetetraacetate and o-phenanthroline. The three BANA (BAPA) hydrolases also had similar molecular weights (∼ 17,500) and different isoelectric points (4.2, 4.3, and 4.7). In addition to the indicated hydrolases, minor components, possessing the same activities but differing in strength of the bond to the inner mitochondrial membrane, molecular weight, and sensitivity to proteinase inhibitors, were detected in the detergent extracts of the SMP. It was concluded that there is a polymorphism of the proteinases associated with the inner mitochondrial membrane