Characterization of the Substrate Specificity of Human Carboxypeptidase A4 and Implications for a Role in Extracellular Peptide Processing

摘要: CPA4 (carboxypeptidase A4) is a member of the metallocarboxypeptidase family. was originally found in screen mRNAs up-regulated by sodium butyrate-induced differentiation cancer cells. Further studies suggested relation between and prostate aggressiveness. In present study, we determined that secreted from cells as soluble proenzyme (pro-CPA4) can be activated endoproteases, such trypsin. Three complementary approaches were used to study substrate specificity CPA4; kinetic analysis performed using new series chromogenic substrates some biologically relevant peptides, cleavage synthetic peptides tested individually, mixture >100 mouse brain examined quantitative peptidomics mass spectrometry-based approach. able cleave hydrophobic C-terminal residues with preference for Phe, Leu, Ile, Met, Tyr, Val. However, not all cleaved, indicating importance additional within peptide. Aliphatic, aromatic, basic P1 position have positive influence on specificity. contrast, acidic residues, Pro, Gly negative position. Some identified (such neurotensin, granins, opioid peptides) been previously shown function cell proliferation differentiation, potentially explaining link Taken together, these suggest functions neuropeptide processing regulation extracellular environment.