Binding of the bidentate inhibitor [3H]HACBO-Gly to the rat brain neutral endopeptidase "enkephalinase"

Abstract

The synthesis and binding properties to rat brain tissue of the enkephalinase inhibitor [3H] N-[(R,S)-3-hydroxyaminocarbonyl-2-benzyl-1-oxopropyl]-glycine ([3H]HACBO-Gly, 45 Ci/mmole) is reported. [3H]HACBO-Gly binding to membranes from various rat brain tissue is saturable (KD = 0.4 +/- 0.05 nM) and linearly related to the amount of tissue. Non specific binding is less than 15% of total binding at the KD concentration. The regional distribution of [3H]HACBO-Gly binding and enkephalinase activity are closely correlated with highest levels in striatum and substantia nigra. The efficiency of inhibitors of various peptidases (thiorphan, captopril, bestatin ...) to inhibit [3H]HACBO-Gly binding or enkephalinase activity are similar. These results indicate that [3H]HACBO-Gly binds selectively to enkephalinase. This compound should help to clarify the localization of the enzyme in the CNS.