Effect of zinc ion on the inhibition of carboxypeptidase A by imidazole-bearing substrate analogues

Competitive inhibitors of carboxypeptidase A, 2-(4-imidazoyl)hydrocinnamic acid (1) and its congeners (2–4) that bear an imidazole ring as the zinc-ligating functionality have been evaluated for their CPA inhibitory activity in the presence of zinc ion to find that the zinc ion augments the inhibitory potency by up to 212-fold.