魚類ミオシンＢの粘性に及ぼす中性塩の影響

Abstract

To study the effect of neutral salts on myosin B (MB) of white croaker and carp, MB (pH 7.0) was kept at a fixed temperature in the range of 2-30°C with various concentrations (0.3-2.0M) of KCl of NaCl and the change in the viscosity was measured as a function of the lapse of reaction time. The decrease in the viscosity number (Zη=1nηr/C) was found to proceed in two first-order steps: an early fast decrease, followed by a slow decrease. As the concentration of salt (M) in the medium increased, the rate (K) for the decrease in Zη as well as the extent (ΔZη) of viscosity decrease both increased. The relationship between the salt concentration (M) and the K values revealed that white croaker MB was more susceptible to salt than carp MB. A similar trend was also observed between the salt concentration (M) and ΔZη. In addition, the increasing rates of K and of ΔZη were found to be the order of LiCl, NaCl, from the highest to the least. The high salt-induced decrease in viscosity of MB occurred quickly even at low temperatures, around 2-15°C, while the inactivation of its Ca-ATPase by salt was detectable only at temperatures, around 2-15°C, while the inactivation of its Ca-ATPase by salt was detetable only at temperatures higher than 20°C.