Quantitative Comparison of the Binding of Various Glycolytic Enzymes to F‐Actin and the Interaction of Aldolase with G‐Actin

The binding to F‐actin of several crystalline rabbit muscle enzymes of glycogenolysis and glycolysis, was investigated in vitro. Under the conditions chosen, no binding occurs in the case of glycogen phosphorylase, phosphoglucomutase, glycerate phosphomutase and enolase. Aldolase, pyruvate kinase and triosephosphate dehydrogenase are strongly bound to F‐actin, whereas lactate dehydrogenase and phosphoglycerate kinase are bound to a lesser degree. The quantitative differences in the affinity to F‐actin are expressed by differences in the determined binding constants. Analytical evaluation of the binding characteristics suggests two binding sites in the case of aldolase and pyruvate kinase. Analytical ultracentrifugation studies and density gradient centrifugation in sucrose revealed a complex formation between aldolase and G‐actin monomer. An average s 20, w value of 9.2 S was obtained for the complex. At higher aldolase concentration, a gelation of the G‐actin was observed which resembles the action of α‐actinin.