Abstract
Effects of sorbitol on the autolysis of mantle muscle of squid was investigated by changing the NaCl concentration and the incubation temperatures. When myofibrils were incubated at 25°C, sorbitol altered the NaCl concentration-dependent profile of autolysis. Sorbitol shifted the autolysis peak toward lower NaCl concentrations, leading to an increase in the autolysis rate at approximately 0.2 M NaCl. It was considered that this rate increase was caused by the solubilization of myofibrils with sorbitol, which exposed the cleavage site of the heavy meromyosin-light meromyosin junction to the enzyme. Sorbitol suppressed autolysis at concentrations above 0.3 M NaCl. When myofibrils were incubated at 35°C, sorbitol markedly enhanced autolysis even in medium containing 0.5 M NaCl. It was considered that this peculiar enhancement in the presence of sorbitol is caused by the stabilization of the proteolytic enzyme itself by sorbitol. Thus, the complicated feature of autolysis in the presence of sorbitol was the result of the combined effects of the following three different functions of sorbitol: (i) suppression of proteolytic activity; (ii) promotion of autolysis by solubilization of the myofibrils; and (ii) stabilization of the proteolytic enzyme.
