Yasushi Ohizumi (1), Kimihiro Matsunaga (1), Keigo Nakatani (1) and Jun'ichi
(1) Department of Pharmaceutical Molecular Biology, Faculty of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980, Japan
(2) Department of Pharmacognosy, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060, Japan
Abstract: 6-O-Acetyl-9-methyl-7-bromoeudistomin D (AMBED) (> 10-6 M), a derivative of eudistomin D, markedly enhanced the superprecipitation and the ATPase activity of skeletal muscle myosin B. In both the superprecipitation and ATPase activity of myosin B, the concentration-response curve for Ca2+ was shifted upwards by AMBED. AMBED did not affect the Ca2+-, K+-EDTA- or Mg2+-ATPase of myosin or the ATPase of actomyosin reconstituted from actin and myosin. These results suggest that AMBED causes an increase in the actomyosin ATPase activity mediated through the elevation of the maximum response to Ca2+, resulting in enhancement of the superprecipitation of skeletal muscle myosin B.
Keywords: 6-O-Acetyl-9-methyl-7-bromoeudistomin D, Superprecipitation, Actomyosin ATPase