[Distribution of creatine phosphokinase isoenzymes (EC 2.7.3.2) in cardiac cells]

The distribution of the creatinephosphokinase isoenzymes in the cardiac cells was studied by way of fractional extraction combined with an electrophoretic analysis of each of the received fractions. At the same time, the content of the creatinephosphokinase isoenzymes was studied in carefully purified preparations of myofibrils and mitochondria. The results of the conducted analysis indicate a heterogenic distribution of the creatinephosphokinase isoenzymes within the cells: about 30% of the cellular activity of the enzyme is contained in the mitochondria (the mitochondrial isoenzyme) 50% is comprised by the fraction dissolved in the cytoplasm (isoenzymes MM, MB and BB), and about 20%--in the myofibrils (isoenzyme MM), 5% of them being extracted only by a 0.9 M KCl solution. The myofibril preparation freed of the mitochondria also contains some important creatinephosphokinase activity (isoenzyme MM) comparable with their ATP-ase activity. The mitochondrial isoenzymes is found only in these structures of the cell.