[Purification and various properties of creatine kinase MM isoenzyme from the human heart muscle].

Homogeneous preparation of creatine kinase MM isoenzyme was isolated from human heart muscle using affinity chromatography on Sepharose containing immobilized Cibachron blue F3G-A. The enzyme was active at a wide range of pH 5.0-8.0 exhibiting maximal activity at pH 6.0-6.7. Dependence of the initial rate of creatine kinase reaction on the ADP concentration at pH 6.6 in presence or absence of Mg2+ did not follow the Michaelis-Menten kinetics, while hyperbolic dependence was found at pH 7.6 and pH 5.2. In presence of Mg2+ Km value for ADP at pH 7.6 and pH 5.2 was decreased 4-fold and 1.3-fold, respectively, whereas Vmax was increased 2-fold and 2.5-fold, respectively. Besides, Km value for Mg2+-ADP at pH 7.6 was 3-fold higher than at pH 5.2, while these Km values were similar for ADP. The data obtained suggest that in human heart functional dissimilarity of creatine kinase MM subunits appears to occur, which is of importance in regulation of transphosphorylation.