On the association of glycolytic enzymes with structural proteins of skeletal muscle

Abstract

1. 1. The effects of protein concentration and ionic strength on the adsorption of the individual glycolytic enzymes to F-actin and F-actin—trypomyosin—troponin have been studied. 2. 2. Appreciable association was demonstrated under conditions of physiological ionic strength and high protein concentration, and tropomyosin—troponin established as an important and generalized component of these interactions. 3. 3. Phosphofructokinase, aldolase, pyruvate kinase, lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate isomerase were strongly bound under these conditions, while triosephosphate isomerase, phosphoglycerate kinase, phosphoglycerate mutase, enolase and hexokinase displayed less adsorption to the structural proteins. 4. 4. The influence of a number of parameters on the adsorption phenomena was examined. Ca 2+ and fructose 1,6-diphosphate increased the adsorption of aldolase, lactate dehydrogenase and pyruvate kinase, while decreasing the adsorption of the enzymes of the constant-proportion group. 5. 5. Of the other major enzymic components of skeletal muscle, creatine kinase, adenylate kinase and malate dehydrogenase showed no adsorption to F-actin—tropomyosin—troponin under the experimental conditions. Some adsorption was evident, however, in the case of aspartate aminotransferase, (NADP) isocitrate dehydrogenase and α-glycerolphosphate dehydrogenase. 6. 6. These results have been discussed in relation to their functional significance and the roles of enzyme compartmentation in the cell.