Inhibition of aminopeptidase I

The inhibition of aminopeptidase I from Eschericia coli Kl2 by several dipeptides, which are not hydrolyzed by the enzyme, has been examined quantitatively. The dissociation constants (Kᵢ) of three of these inhibitors with the enzyme have been determined. An affinity chromatography medium was synthesized by linking L-leucyl-L-proline through its carboxyl group by a thioester linkage to aminoalkyl-agarose. The inhibitory properties of L-leucylprolyl-agarose toward aminopeptidase I were much greater than those of L-leucylproline in solution. The behavior of aminopeptidase I on L-leucylprolyl-agarose columns is described.