Localization of the thiorphan‐sensitive endopeptidase, termed enkephalinase A, on glial cells

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Abstract
Degradation of tritiated Leu‐enkephalin was studied in cultures of primary astrocytes from rat brain. The incubation experiments with a cell suspension revealed Tyr as the main tritiated metabolite; however, Tyr—Gly—Gly and Tyr—Gly were detectable as well. Using a crude membrane prepartion of the astrocytes, we found about equal amount of Tyr and Tyr—Gly—Gly but only trace quantities of Tyr—Gly. The production of Tyr was completely inhibited by bestatin, an inhibitor of aminopeptidases, that of Tyr—Gly—Gly by thiorphan, a specific inhibitor of enkephalinase A. The results prove the ability of glial cells to degrade enkephalin by aminopeptidase and a membrane‐bound enkephalinase A.