Angiotensin-converting enzyme, enkephalinase A and aminopeptidases in the breakdown of enkephalin--studies in cell cultures.

Neuroblastoma cells (N1E-115) and glial cells possess aminopeptidases, dipeptidyl carboxypeptidases and dipeptidyl aminopeptidases, which are located in the plasma membranes. Neuronal cells possess angiotensin-converting enzyme (ACE), which splits the Gly-Phe bond and generates Tyr-Gly-Gly from enkephalin. They have no enkephalinase A. In contrast, glial cells possess enkephalinase A but no ACE. Not only the dipeptidyl carboxypeptidases on neuronal and glial cells are different. These cells have aminopeptidases which have to be distinguished as well. This differentiation is made by using bestatin as an aminopeptidase inhibitor and reveals peptidases of high and poor bestatin-sensitivity.