The influence of habitat water temperature on the kinetic properties of Ca2+-and Mg2+-ATPase of myofibrils from marine fishes.

Abstract

The Michaelis constants (Km), maximum velocity (Vmax), and temperature dependence of myofibrillar Ca2+-and Mg2+-ATPase were examined using fishes in the sea around Sakishima Islands inhabiting at 28°C and in the Yellow Sea inhabiting at 9°C. The Km values of myofibrillar Ca2+-ATPase were lower with fishes from Yellow Sea than with fishes from Sakishima Islands, while Km values of myofibrillar Mg2+-ATPase did not differ between fishes from Yellow Sea and Sakishima Islands, The Vmax levels of myofibrillar Ca2+-ATPase did not differ between fishes from Yellow Sea and Sakishima Islands, but those of myofibrillar Mg2+-ATPase were higher in fishes from Yellow Sea than in fishes from Sakishima Islands at reaction temperatures of 10°C and 30°C. Temperature dependency of myofibrillar Ca2+-ATPase activity in a saturated substrate concentration was not different between fishes from Yellow Sea and Sakishima Islands, but that of myofibrillar Mg2+-ATPase activity was smaller with fishes from Yellow Sea than with fishes from Sakishima Islands. The differences in Mg2+-ATPase with varying habitat temperature indicate the existence of an efficient mechanism for locomotory activity in fishes living in lower habitat temperatures.