Heterogeneous distribution of enkephalin-degrading peptidases between neuronal and glial cells.

Cultured neurones, astroblasts and astrocytes from murine brain have been screened with specific tests for the presence of peptidases capable of degrading enkephalin. Bestatin-sensitive aminopeptidases represent the major enkephalin-degrading activity in all cases. The dipeptidylaminopeptidasic activity is much higher in the neuronal than the glial cultures, whereas the opposite is true for the metallopeptidase called "enkephalinase". Only trace amounts of the dipeptidylcarboxypeptidase "angiotensin-converting enzyme" have been found. We conclude that bestatin-sensitive aminopeptidases on nerve cells are probable candidates for enkephalin-inactivating enzymes, whereas the "enkephalinase" on glial cells more likely serves a scavenger function.