Catalytic properties of protein kinase system from rabbit myocardial sarcolemma

: High-purified sarcolemma vesicles possessing endogenic protein kinase activity (EC 2.7.1.37) are isolated from the rabbit myocardium. Membrane-bound protein kinase catalyzed phosphorylation both of endogenic sarcolemma proteins and exogenic substrate--histones. Protein kinase was 1.4 times activated when affected by optimal concentration of 3' : 5'-AMP (10(-6) M). The value of seeming Km was 3.2 . 10(-6) M for ATP, and 0.66 mg/ml--for histone H1. In vesicles of sarcolemma endogenic protein kinase phosphorylated seven protein substrates with the molecular mass 220 000, 145 000, 110 000, 84 000, 43 000, 22 000 and 16 000. Exogenic soluble protein kinase produced the highest additional stimulation of phosphorylation for proteins with molecular mass 22 000 and 16 000.