Enkephalin convertase

Carboxypeptidase H (EC 3.4.27.10 carboxypeptidase H enkephalin convertase) is not fully characterized, and may be a metalloproteinase. Substrates of this enzyme, found in cell membranes and secretory vesicles, include enkephalins, bradykinin and ATRIAL NATRIURETIC peptide. Two mercapto inhibitors used are MERGETPA (MGTA) and GEMSA, but they are not very selective. 

Figure 3 Cysteine protease and subtilisin-like protease pathways for proneuropeptide processing. Distinct cysteine protease and subtilisin-like protease pathways have been demonstrated for pro-neuropeptide processing. Recent studies have identified secretory vesicle cathepsin L as an important processing enzyme for the production of the endogenous enkephalin opioid peptide. Preference of cathepsin L to cleave at the NH2-terminal side of dibasic residue processing sites yields peptide intermediates with NH2-terminal residues, which are removed by Arg/Lys aminopeptidase. The well-established subtilisin-like protease pathway involves several prohormone convertases (PC). PC1/3 and PC2 have been characterized as neuroendocrine processing proteases. The PC enzymes preferentially cleave at the COOH-terminal side of dibasic processing sites, which results in peptide intermediates with basic residue extensions at their COOH-termini that are removed by carboxypeptidase E/H.

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