[Nature of the changes in water-soluble enzyme activity in the exposure of muscles to harmful agents. III. A study of creatine kinase extractability from intact and altered muscles].

Binding of creatine kinase (CrK) in intact and thermally altered (15 minutes at 37 and 38 degrees C) skeletal muscles of frogs (Rana temporaria L.) was studied according to CrK extractability from muscles. The CrK activity in actomyosin isolated from muscles and its changes in thermally altered actomyosin were detected. Solutions of KCl (0.075, 0.15, 0.3 and 0.6 M) and of NaF (0.15 M) extract additional amounts of CrK from intact and altered muscles. Inhibiting effects of KCl, NaF and K2HPO4 on CrK in muscle extract were found. The latter exerts the most pronounced inhibiting effect, which prevents it from being used for CrK extraction purposes. Among the structural components of muscle that bind CrK actomyosin was detected. The actomyosin isolated from muscles revealed CrK activity. CrK in actomyosin gel is much more stable to thermal effect than that in a water extract of muscle. Such a thermostabity of CrK within the system of the whole muscle cell may apparently result from its being bound to actomyosin.