Thiamine triphosphatase activity of myosin and accelerating effect of thiamine di- and tri-phosphates on superprecipitation of actomyosin.

Abstract

TTP accelerated ATP-induced superprecipitation of actomyosin in as low a concentration as 30 μM and decreased light scattering by actomyosin. These effects could also be observed in the same way, but to a lesser degree, by addition of TDP. Myosin was able to hydrolyze TTP to TDP, but some important differences were confiirmed between myosin TTPase and ATPase. Myosin TTPase was inhibited by actin and showed a much larger Km than that of ATPase. TTP significantly inhibited myosin B ATPase and ATP greatly inhibited myosin B TTPase. These findings suggest that the accelerating effect of TDP and TTP may be due to the binding of thiamine phosphate to the regulatory site of myosin followed by a change in its physical chemical property, rather than due to the competitive binding of thiamine phosphate to the catalytically active site of myosin. © 1975, Center for Academic Publications Japan. All rights reserved.