Purification of mitochondrial creatine kinase. Biochemical and immunological characterization.

Mitochondrial creatine kinase was purified from canine myocardium. The preparation exhibited a positively charged isoenzyme free of other creatine kinase isoenzymes and on sodium dodecyl sulfate gel exhibited a single protein band. Amino acid composition showed mitochondrial creatine kinase to be different from that of MM or BB creatine kinase and did not hybridize with the M or B subunits of the cytosolic forms. Antiserum was developed to mitochondrial creatine kinase which did not cross-react with cytosolic creatine kinases. Antiserum to cytosolic creatine kinase exhibited no reaction to mitochondrial creatine kinase. Utilizing the specific antiserum, a radioimmunoassay was developed for the specific detection of mitochondrial creatine kinase. Thus, mitochondrial creatine kinase was purified and shown to be comprised of a unique subunit which is biochemically and immunologically distinct from the cytosolic creatine kinases.