南極産オキアミの肝すい臓たんぱく質分解酵素によるアクトミオシンの消化性

Abstract

A change in the muscular protein of Antarctic krill with its digestive protease of hepatopancreas has been studied by measuring the viscosity of actomyosin. Taking account of the instability of actomyosin, the decrease in viscosity was assayed in the presence and absence of sorbitol. The decrease in viscosity was thus found to proceed in two distinct stages: a fast first-order decrease in an early stage, followed by a relatively slow first-order decrease. The first-order rate constant (K') at the early stage was then used as a measure of digestibility of actomyosin. In the presence of 1.5 M sorbitol, actomyosin was digested with various concentrations of crude protease and at various temperatures. It was thus found that actomyosin of krill was several times more rapidly digestible than that of carp was. When the digestion was performed in the presence of various concentrations of sorbitol (0-2.5 M), the rate constant (K') was found to decrease with increasing molarity of sorbitol. From the linear relation between log K' and sorbitol (M), the K' value for actomyosin of krill without sorbitol was theoretically obtained. SDS-gel electrohporetic patterns of these digests showed that myosin heavy chain of krill was rapidly decomposed by its digestive protease, but this decomposition was effectively prevented by sorbitol.