[The causes of the nonuniform thermostability of Mg-ATPase and of the contractility of muscle models]. / Prichiny neodinakovoi teploustoichivosti Mg-ATFazy i sokratimosti myshechnykh modelei.

With longer periods of preliminary heat-treatment of actomyosin suspension the decrease in the rate of superprecipitation (SPP) is followed by that in the extent of SPP, and, finally, in the Mg-ATPase activity. A similar uncoupling of mechanical and enzymatic activities is observed when the ratio between the native and the inactivated myosin in reconstructed actomyosin varied. This uncoupling is supposed to result from the formation during heat-treatment of myosin bridges incapable of dissociating in the presence of Mg-ATP. The bridges affect largely the mechanical properties of actomyosin, and in a lesser degree, its enzymatic properties.