Normal and diabetic malic enzyme: a biochemical comparison.

The ability of insulin to influence the specific activity of hepatic malic enzyme was examined by comparing the biochemical properties of hepatic malic enzyme isolated from normal and diabetic rats. Even though these two enzyme species possess very different specific activities, they appeared biochemically identical upon two-dimensional gel electrophoresis, Western blot analysis, and in mixing experiments. The only major difference observed for the two enzyme molecules was in their respective Km and Vmax apparent values. These results appeared to indicate that the two enzyme molecules were structurally identical but functionally different. Suggestive evidence showed that this functional difference was the result of substrate inhibition of the diabetic malic enzyme molecule.