Proenkephalin-Derived Peptides in the Carotid Body

The heterogeneity of opioid peptides in different structures of the organism is achieved by two mechanisms: (1) the expression of the opioid precursors and (2) the posttranslational processing of these precursor molecules. The latter mechanism is the result of sequential actions by different enzymes, including endopeptidases, exopeptidases, and other nonhydrolyzing enzymes (1). The carboxypeptidase E (CPE; also called H) is an exopeptidase specific for basic residues of the carboxy terminal of a great number of peptides and has been defined as a neuropeptide-processing enzyme (2).