No evidence for enkephalinase A on neuronal cells

It is generally assumed that enkephalinase A, a highly thiorphan-sensitive dipeptidylcarboxypeptidase cleaving the Gly-Phe bond during enkephalin degradation, is bound to the neuronal membrane. To clarify the localization of the enzyme, we used three neuron-like models (neuroblastoma cells N1E-115, bulk prepared neurons and neurons in primary culture) and three glial models (astrocytes from rat brain and from chick embryo brain in primary culture and bulk prepared glial cells). After incubating membranes and cells with (Leu5)-enkephalin, we found that, contrary to the present opinion, the enkephalinase A is located on the glial cells, whereas the neuronal cells possess angiotensin-converting enzyme.