Conformational energies of substrates and inhibitors for carboxypeptidase A: stereoelectronic effect.

Because of the complexity involved in binding of a ligand to an enzyme the conformational preference of the bound ligand has not been well understood yet. We have examined the conformational energies of ligands for carboxypeptidase A using ab initio calculations. Considering the large stereoelectronic effect of 4-5 kcal/mol, the energetic preference of the unbound ligand conformers which arises from the stereoelectronic effect appears to play a significant role in determining the bound ligand conformations.