Neurokinin B is hydrolysed by synaptic membranes and by endopeptidase‐24.11 (‘enkephalinase’) but not by angiotensin converting enzyme

Abstract

The major site of hydrolysis was the Gly⁸‐Leu⁹ bond. Angiotensin converting enzyme (peptidyl dipeptidase A, EC 3.4.15.1) from pig kidney hydrolysed substance P releasing the C‐tenninal tripeptide Gly‐Leu‐MetNH₂ but failed to hydrolyse neurokinin B. Pig brain striatal synaptic membranes hydrolysed neurokinin B producing a similar pattern of products as did endopeptidase‐24.11. Substantial inhibition of this activity was achieved with the selective inhibitor phosphoramidon. A combination of phosphoramidon and bestatin abolished the hydrolysis of neurokinin B by synaptic membranes. Thus, a bestatin‐sensitive aminopeptidase may play a role in the synaptic metabolism of neurokinin B in addition to endopeptidase‐24.11. This aminopeptidase appears to be distinct from aminopeptidase N (EC 3.4.11.2).