イカ外套膜筋アクトミオシンのATPase活性に関する研究〔英文〕

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The actomyosin ATPase of the obliquely striated squid mantle muscle, which has many characteristic properties in its solubility, electrophoretic behavior and lability as reported previously, was characterized. The ultracentrifugal patterns of squid actomyosin showed its peaks in aggregated states, while, on SDS-acrylamide gel electrophoresis, amount of actin and myosin accounted for 70% of total proteins. Paramyosin and tropomyosin were found as contaminants which are not readily removable at present. The ATPase activity measured in tris-maleate buffer at 0.05 or 0.6 ionic strength (I) and at 20°C was stimulated markedly with Ca2+ and moderately with Mg2+, but depressed with EDTA. [Stimulation by both Ca2+ and Mg2+ was most effective at 32 ram.] In the presence of Ca2+, the activity showed 2 maxima at pH 7.0-7.5 and pH 9.0, while, with Mg2+ present, it leveled off beyond pH 6.8-7.0. The activity was highest at I=0.25. The presence of membrane and mitochondrial ATPase was refuted since neither ouabain nor oligomycin depressed the activity. The stimulating effect of Mg2+ appears to he characteristic of the squid actomyosin ATPase.
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