Quantum chemistry analysis of the mechanism of action of proteolytic enzymes. I. The state of the cleavable bond of substrates and intermediates

Electronic parameters of amide and ester bonds in some compounds, modelling substrates of proteolytic enzymes, and electronic properties of corresponding tetrahedral compounds, which are intermediates of the hydrolytic reaction, were calculated by the CNDO/2 method. The nature of substituents and the formation of the hydrogen bond by the carbonyl oxygen atom were shown to have no sufficient influence on the charges and bond orders of the amide group. The dramatic dependence of the amide electronic state from the distort degree of its planar structure was found. The resonance stabilization was shown to be absent in the bicyclic beta-lactams. The pK alpha values of the amide nitrogen atom were calculated at various hybridization states in amides.