Cooperative Effect of Carboxylic Acid and Sugar against Freeze Denaturation of Fish Myofibrillar Protein

Abstract

The first order rate constant (k_D) at the oarly phase of freeze inactivation of carp myofib-rillar Ca-ATPase was determined in the presence of varied concentration of several carboxylic acid.
From the linear relation between log k_D and the morality (M) of carboxylic acid, the protective effect (denoted as E) was estimated as a decrease in log k_D/M of each carboxylic acid.
The effect was thus found to become stronger in the order of formate, acetate, glycine, succinate, tartrate, gluconate, glutamate.
The rank in protective effect of carboxylic acid against freeze denaturation, fairly coincided with that of the same acid against thermal denaturation of myofibrils.
The joint protective effect of carboxylic acid with sugar and amino acid was also studied by the same manner. The variation in log kD showed that the cooperative effects were nearly additional for all pair combinations from sucrose, acetate, and glutamate and for those of sucrose, acetate, and glutamate.
A discussion followed on a possible mechanism for cooperative protection by carboxylic acids with sugar and amino acid against freeze denaturation on myofibrillar protein.