Tautomeric Equilibria and pi-Electron Delocalization for the Substrate(Pyruvate)and Inhibitor(Oxamate)of Lactate Dehydrogenase-DFT Studies

摘要

Keto-enol tautomerism for the substrate(pyruvate)of lactate dehydrogenase(LDH)and amide-iminol tautomerism for its inhibitor(oxamate)were studied at the DFT(B3LYP)/6-31++G(d,p)level.Both anions(and also both radicals)prefer the C=O forms,i.e.the keto and amide form,respectively.The OH forms(enolpyruvate and iminoloxamate)have higher Gibbs free energies.Their amounts in the tautomeric mixtures are larger than 0.01% for anions and lower than 0.001% for radicals.pi-Electron delocalization for OCO fragments is greater than that for XCO fragments for both anions and radicals.