Peptidases involved in the inactivation of exogenous and endogenous enkephalins.

Among the various cerebral enzyme activities able to hydrolyse the enkephalins into inactive fragments only two seem responsible for the metabolism of the endogenous opioid peptides: a dipeptidylcarboxypeptidase ("enkephalinase"), and a bestatin-sensitive aminopeptidase. Their inhibition by thiorphan and bestatin results in an antinociceptive effect observed in tests in which the nociceptive stimulation is probably accompanied by a concomittent release of enkephalins.