Effects of magnesium and calcium ions on the adenosinetriphosphatase activity of insect actomyosin at low ionic strength.

Abstract 1. 1. The Mg-enhanced ATPase activity of insect actomyosin was shown to be greatly dependent upon the free Ca 2+ concentration in the assay system. The effect of Mg 2+ and Ca 2+ on the ATPase activity was studied at varied KCl concentration. 2. 2. The requirement of Mg 2+ , not of Ca 2+ , for the onset of superprecipitation on insect actomyosin was demonstrated.