Action of neutral metalloendopeptidase ("enkephalinase") on beta-endorphin

Human beta-endorphin was digested by neutral metalloendopeptidase from rabbit kidney and the products were isolated and identified. Based on the structure and yield of the fragments, the major cleavage sites were identified with the Leu17-Phe18, Gly3-Phe4, Pro13-Leu14 and Ile22-Ile23 peptide bonds of the beta-endorphin structure. The cleavage of the Leu17-Phe18 bond appears to be the rate-limiting step of the enzymic conversion similarly to the previously proposed pathways of beta-endorphin degradation by brain homogenates and synaptic membranes.