Kinetic and molecular modeling of nucleoside and nucleotide inhibition of malate dehydrogenase

We studied the inhibition of mitochondrial malate dehydrogenase (mMDH) by the nucleotides cAMP, AMP, ADP, ATP. The experimental kinetic studies showed that the nucleotides were competitive inhibitors and that cAMP was probably the most potent inhibitor. To explain these observations, we used molecular modeling to determine the location, orientation, and relative binding energy of the nucleotides to mMDH. The order of the calculated binding energies, from lowest (most favorable) to highest, was cAMP, AMP, ADP, and ATP, which corresponded somewhat to the order of the experimentally determined inhibition constants.