Kinetic analysis on the substrate specificity of 3‐isopropylmalate dehydrogenase

Abstract

Substrate specificity of 3‐isopropylmalate dehydrogenase is analyzed using a series of synthetic (2R,3S)‐3‐alkylmalates. Each analog with hydrogen, methyl, ethyl, isopropyl, isobutyl, tert‐butyl, and isoamyl group on C‐3 functions as a substrate, implying a broad substrate specificity of the enzyme toward alkylmalates. The incremental binding energy of the isopropyl group of 3‐isopropylmalate to the enzyme is estimated to be 3.55 kcal/mol, the rather small value supporting the broad specificity. Although the enzyme shows a broad specificity toward the alkylmalates, it does not show activity with isocitrate which has a negatively charged carboxymethyl group instead of the alkyl groups.