Differential recognition of "enkephalinase" and angiotensin-converting enzyme by new carboxyalkyl inhibitors

Abstract

New carboxylalkyl compounds derived from Phe-Leu and corresponding to the general formula C6H5CH2CH(R)COL. Leu with R = COOH, 3 R = CH2 COOH, 4, R = NHCH2COOH, 5, R = NH(CH2)2COOH, 6, have been found to inhibit the breakdown of the Gly3Phe4 bond of [3H] Leu-enkephalin or [3H] D. Ala2-Leu-enkephalin resulting from the action of the mouse striatal metallopeptidases : "enkephalinase" or angiotensin-converting enzyme (A.C.E.). The carboxyl coordinating ability of the Zn atom seems to be significantly higher in ACE than in "enkephalinase". Moreover, IC50 values against "enkephalinase" were found in the same range whatever the length of the chain bearing the carboxyl group whereas a well-defined position of this group with respect to the Zn atom is required for strong ACE inhibition. These features suggest a larger degree of freedom of the carboxyalkyl moieties within the active site of "enkephalinase". Therefore the differential recognition of active sites of both peptidases leads to : i) N(carboxymethyl)LPheLLeu, 5, a competitive inhibitor of "enkephalinase" (KI = 0.7 μM and ACE (KI = 1.2 μM) which could be used as mixed inhibitor for both enzymes; ii) N[(R,S)2carboxy, 3benzylpropanoyl]LLeucine, 3, a full competitive inhibitor of "enkephalinase" (KI = 0.34 μM) which does not interact with ACE (IC50 > 10,000 μM). This compound can be considered as the first example of a new series of highly potent and specific "enkephalinase" inhibitors. © 1982.