Some characteristics of beta-naphthyl triphosphate as a substrate of heavy meromyosin. F-actin-inactivated hydrolysis showing initial burst.

The initial burst of Pi liberation was found in the hydrolysis of beta-naphthyl triphosphate (beta-NapP3) by heavy meromyosin (HMM) in the presence of Mg ions as well as in the hydrolysis of ATP. However, unlike that of ATP, the steady-state hydrolysis of beta-NapP3 by HMM was inhibited by the addition of F-actin to the reaction solution. Although the possession of an initial burst-like property during interaction of a substrate and myosin is believed by many investigators to be a key factor in F-actin activation of substrate hydrolysis in vitro and in the molecular mechanism of muscle contraction, the above results suggest that this is not generally true. beta-NaP3 did not induce superprecipitation of actomyosin solution and suppressed ATP-induced superprecipitation.