コイ筋原繊維Ca2+-およびMg2+-ATPaseの諸性質に及ぼう棲息水温の影響

The effects of habitat temperature on the temperature dependence, Michaelis constants (Km), and maxim velocity(Vmax)of myofibrillar Ca2+- and Mg2+-ATPase were experimentally studied using carps reared at 10°C(group L)and 30°C(group H)for different lengths of time. The tem-perature dependences of Mf Ca2+-and Mg2+-ATPase rose in both groups L and H with a longer rearing period, although the degree of increase differed for Mf Ca2+-and Mg2+-ATPase. The degree in Mf Ca2+-ATPase was larger in group L than in group H, while the degree in Mf Mg2+-ATPase was smalley in group L than in group H. Km values of both Mf Ca2+-and Mg2+-ATPase were smaller slightly in group L than in group H at reaction temperatures of 5°C to 30°C in the former, and 10 to 20°C in the latter. The Vmax level of Mf Ca2+-ATPase was higher in group L than in group H at 30°C, while the opposite was observed at 10°C. The Vmax level of Mf Mg2+-ATPase, however, was higher in group L than in group H at all reaction temperatures from 5°C to 30°C. We consider that these findings in Mf Mg2+-ATPase indicate the existence of an efficient mechanism for the production of energy in fishes living in low habitat temperatures.