Enzyme kinetics of a highly purified mitochondrial creatine kinase in comparison with cytosolic forms

Summary Mitochondrial creatine kinase (CK) purified from canine myocardium showed a single protein band on SDS-PAGE and was free of MMCK. Its amino acid composition was different than MMCK or BBCK and did not react to antiserum to MMCK or BBCK. Using purified mitochondrial, MM and BBCK, the velocity of reaction (V) was estimated for creatine phosphate (CP), creatine (C), adenosine triphosphate (ATP) and adenosine diphosphate (ADP) over a wide range of concentrations including those at V_max. The values for K_m (mM/L) derived from Lineweaver-Burke plots are shown: The affinity of mitochondrial CK for C is much greater than MMCK which is compatible with the energy shuttle hypothesis, namely ATP is converted by mitochondrial CK to CP, and then diffuses to the myofibril for conversion to ATP for utilization.