Interaction of Fish Muscle Glycolytic Enzymes with F-Actin and Actomyosin

Abstract

The binding of fish muscle glycolytic enzymes with F-actin and actomyosin was studied in vitro under various conditions. The binding of glucosephosphate isomerase, phosphoglycerate kinase and enolase with the myofibrillar proteins was weak, while that of aldolase and glyceraldehyde-3-phosphate dehydrogenase was strong. The latter enzymes showed the ratio of the unbound to total enzyme ranging from 9-50%, when mixed with F-actin or actomyosin. The recovery of bound enzyme ranged from 61 to 86% for aldolase and from 60 to 92% for glyceraldehyde-3-phosphate dehydrogenase.
The enzyme-myofibrillar protein binding was depressed by the increase in reaction pH, KCl or Ca²⁺ concentration. In the presence of 150mM KCl or 50mM Ca²⁺, the binding was inhibited almost completely. Glycolytic metabolites also influenced the binding. Fructose-l, 6-bisphosphate and 2, 3-bisphosphoglycerate caused a marked adsorption-hindrance for aldolase at a concentration of 1mM. The results obtained could account for the enzyme-specific extractability from fish muscle.