Abstract
To clarify the mechanism of activation by lecithin of the actomyosin ATPase from fish muscle, the effect of lecithin on the interaction of actomyosin with ATP was examined.
1) The marked structural change of actomyosin induced by the addition of lecithin was observed in the presence of ATP, as judged by a more drop in the relative intensity of light scattering at 90°.
2) By the treatment of actomyosin with phospholipase C, the substrate concentration curve-the ATPase activity showed the sigmoidal shape.
3) The enhancing effect of lecithin on the actomyosin ATPase activity was lost as a result of storage of the preparation and treatment with NTP, without loss of the original enzyme activity. On the other hand, although pCMB inhibited the ATPase activity, the ATPase was susceptible to lecithin. From these results, it was assumed that the sensible site to lecithin on the actomyosin preparation presumably is different from that to ATP.
