Abstract: The model enzymatic inhibition mechanism by inhibitor oxamate has been studied at the HF/321G level. All the conclusions can be summarrized as follows:(a)the conformations of the optimized model inhibitor oxamate and substrate are much more similar with each other,which leads to an unidentified action of the substrate and inhibitor by Llactate dehydrogenase(LDH); (b)the electronic distribution of the inhibitor is favorable for the combination of oxamate to LDH active site; (3)the space of LDH active site is contracted by the inducedfit interaction between the LDH and the inhibitor;(4) the molecular fragment methyl of substrate and the residue Gln102 of LDH probably play an important role in the enzymatic reaction.

Key words: L-lactate dehydrogenase, Enzymatic reaction, Enzymatic inhibition, Ab initio, Molecular fragment