Effect of Inorganic Pyrophosphate on the Interaction between Actomyosin and Adenosinetriphosphate

　Actomyosin, the contractile protein in muscle, undergoes remarkable change in its shape by ATP and, at the same time, possesses the enzymatic activity which catalyses the hydrolysis of end group of ATP（1〜3）．The interaction between ATP and actomyosin has been studied by many investigators in order to obtain the information of mechanism of muscular contraction（4〜8）．

　The recent tendency in the biochemistry of muscle is to consider the enzymatic hydrolysis of ATP as the energy-yielding reaction of muscular activity, but it is not yet clear how the physical change of actomyosin is caused．