A transition state analog for two pyruvate metabolizing enzymes, lactate dehydrogenase and alanine dehydrogenase

The synthesis of 5-(2-oxalylethyl)-NADH, a reduced nicotinamide adenine dinucleotide (NADH) derivate with pyruvate covalently attached to the 5 position of the dihydronicotinamide ring over an additional methylene group has been described previously (Trommer, W.E., Blume, H., and Kapmeyer, H. (1976) Justus Liebigs Ann. Chem., 848). In the presence of lactate dehydrogenase, the dihydropyridine ring of this coenzyme-substrate analogue is oxidized and the carbonyl function of the side chain is reduced to the corresponding L-hydroxy derivative with a maximum velocity of 1/3000 of the natural reaction. This reaction is intramolecular as shown by competition experiments with pyruvate. 5-(2-oxalylethyl)-NADH (pyr-NADH) appears to be a true transition state analogue, proving its postulated structure. Pyr-NADH is high specific for this enzyme as demonstrated by the facts that (1) D-lactate dehydrogenase does not catalyze the intramolecular redox reaction, although the substrate moiety of pyr-NADH is reduced in the presence of NADH; (2) when tested with malate dehydrogenase, alcohol dehydrogenase, glyceraldehyde phosphate dehydrogenase,glycerate dehydrogenase, and glycerol dehydrogenase pyr-NADH is not even oxidized in the presence of the corresponding substrates. However, a great similarity between the transition states of the reduction of pyruvate catalyzed by lactate dehydrogenase and alanine dehydrogenase could be shown. Alanine dehydrogenase catalyzes the intramolecular redox reaction as well. In the presence of ammonium ions, pyr-NADH is transformed to 5-(3-carboxyl-3-aminopropyl)-NAD+.