The hydrolysis of purine and pyrimidine nucleoside triphosphates by myosin.

It is well established that myosin will catalyze the hydrolysis of inosine triphosphate’ (l-3) as well as ATP. Even catalysis of inorganic triphosphate hydrolysis has been observed (4, 5).2 It has been reported recently (7) that uridine triphosphate is rapidly hydrolyzed in the presence of crystalline myosin, and previously unpublished experiments3 showed that synthetically made UTP4 is rapidly hydrolyzed by the heavy component of meromyosin (3,8,9). The affinities of the enzyme for ATP, ITP, UTP, and relative velocities of hydrolysis of the same nucleotides have recently been examined by Blum (10). In addition, a report has appeared on the contraction of actomyosin gels in the presence of GTP and UTP (11). Recent communications (12-14) have demonstrated that, in addition to the classical activation of myosin ATPase by Ca++, an even more striking activation is obtained with ethylenediaminetetraacetic acid (Versene, etc.). The present report shows that guanosine triphosphate, cytidine triphosphate, and adenosine tetraphosphate (15) are also hydrolyzed by myosin ATPase, and it presents some observations on the characteristics of hydrolysis in the presence of Ca or EDTA with special reference to the structure of the nucleoside triphosphates.