The importance of changes in ATP and ADP concentrations in the development of the phasic superprecipitation of actomyosin.

It has been shown previously that at physiological K+-concentrations the development of superprecipitation has a phasic character. Studying the reason of this effect, by the use of beta-32P-ADP ATP-regeneration from ADP was detected during the first phase of superprecipitation. Myokinase activity of actomyosin may be responsible for the appearance of this first phase of turbidity change of actomyosin suspension. Myokinase contributes to the stabilization of an ATP/ADP ratio within narrow limits. During the first phase of superprecipitation the ATP/ADP ratio is between these limits, while during the second phase the ratio has a low value. This phasic evolution of superprecipitation is, probably connected with the physiological functional state of the muscle (contraction or rigour).