PROTEINS IN FISH MUSCLE: 16. ADENOSINETRIPHOSPHATASE ACTIVITY OF COD MYOSIN AND ACTOMYOSIN

Abstract

The adenosinetriphosphatase (ATPase) activities of actomyosin extracts of prerigor and postrigor cod muscle, and of myosins prepared from them by ultracentrifugation in the presence of ATP, have been measured at ionic concentration 0.1 and pH 7.3. The actomyosin ATPases were strongly activated by Mg⁺⁺, while those of the myosins were suppressed by Mg⁺⁺, in agreement with corresponding rabbit skeletal muscle proteins. Ca⁺⁺ion also moderately activated the actomyosin ATPases, but had little effect on the myosin ATPases. When actomyosin was precipitated by dilution in the presence of ATP and Mg⁺⁺, the characteristic activation by Mg⁺⁺was lost. The myosin ATPases were very labile.