INSULIN AND FRUCTOSE REGULATE MALIC ENZYME-ACTIVITY BY DIFFERENT PROCESSES

A comparison of the regulatory process controlling hepatic malic enzyme activity following treatment of diabetic rats with insulin or with a high fructose diet demonstrated several important differences. Insulin treatment caused a 50-fold increase in activity, due to a 12-fold increase in enzyme quantity and a 4-fold increase in specific activity (U/nmol). Dietary fructose caused a 3-fold increase in enzyme activity, due to a 3-fold increase in enzyme quantity, with no change in the specific activity of the enzyme. While fructose initiated a minor increase in malic enzyme activity, insulin was more effective, causing a substantially greater increase in enzyme activity and activating a hormone specific alteration in the catalytic activity of each enzyme molecule.