Hydrolysis of enkephalins by human converting enzyme and localization of the enzyme in neuronal components of the brain.

Homogeneous human CE hydrolyzed Met5-enkephalin fastest of the biologically active substrates tested. The inactivation of Met5-enkephalin was inhibited by antiserum to Ce and by specific inhibitor of CE (MK 421; I50 = 8 x 10(-9)M). Direct radioimmunoassay of CE extracted from basal ganglia indicated immunological identity of lung, kidney, and brain CE. Immunocytochemically, CE was demonstrated in the choroid plexus, where the enzyme appears to be bound, as in kidney and gut, to the surface of the epithelial cell bathed by luminal fluid. CE immunoreactivity in brain parenchyma was demonstrated in neuronal elements in the hippocampus, hypothalamus, neocortex, globus pallidus, and substantia nigra.