Immunochemical characterization of carboxypeptidase B-like peptide-hormone-processing enzyme.

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Abstract
Specific rabbit antisera against purified bovine pituitary carboxypeptidase processing enzyme (also referred as enkephalin convertase) were prepared and characterized. The antisera recognized both the purified soluble and the membrane-bound forms of the enzyme with equal affinity, suggesting that these 2 forms of the enzyme may possess many regions of structural homology. Since the antisera did not crossreact with carboxypeptidases B, N, A, Y and P, the carboxypeptidase processing enzyme may be a structurally distinct form of carboxypeptidase. Carboxypeptidase immunostaining, as seen by light microscopy, was found throughout the rat brain and in bovine adrenal medulla, reflecting the widespread distribution of neuropeptides. EM immunocytochemistry of rat paraventricular nucleus and other brain areas showed that the enzyme was present in some dendrites and nerve terminals, which contain storage vesicles. Evidently, this carboxypeptidase is involved in the processing of many peptide hormone precursors.