魚類筋肉構成たんぱく質に関する研究-XIII

Abstract

The effect of temperature on the denaturation of actomyosin prepared from carp dorsal muscle was investigated by measurement of Ca2+-ATPase activity and solubilities. Factors involved in the denaturation, which are salt (KC1) concentration, pH of the solution and the presence of sugar compounds, were tested. 1. The denaturation of actomyosin ATPase by incubation at 35°C proceeded at a uniform rate as protein concentration increased above 5 mg/ml, while it accerelated as the protein concentration decreased below 4 mg/ml. 2. To obtain a uniform protecting effect of sugar compounds on the denaturation of actomyosin ATPase by incubation at 35°C, it was necessary to add sugar compounds as 20 times the actmyosin content on a weight basis. 3. The protecting effect of sorbitol on the denaturation of actomyosin ATPase by incubation at 35°C was higher than that of sucrose at all KCI concentrations and the effect of sorbitol increased at lower KCI concentrations. Conversely, the effect of sucrose on the denaturation decreased at lower KCI concentration after prolonged incubation. 4. In comparing the protecting effect of some sugar compounds on the denaturation of actomyosin ATPase in 0.6 M KCI, pH 6.8 by incubation at 35°C, no marked differences were found with sorbitol, xylitol, glucose, and mannitol but the effect of sucrose was slightly inferior. 5. The first order rate constant of denaturation of carp actomyosin ATPase in 0.6 M KCI -20 mM Tris-maleate solution at 35°C was found to be 1.44×10-4. sec-1 at pH 6 and 0.44 ×10-4. sec-1 at pH 7 and 8, respectively. An efficient protective effect of sorbitol on the denaturation of actomyosin ATPase was observed at pH 7 as well as pH 8, while the effect at pH 6 was found to be inferior.