Neuropeptide Y, B‐type natriuretic peptide, substance P and peptide YY are novel substrates of fibroblast activation protein‐α

Fibroblast activation protein‐α (FAP) is a cell surface‐expressed and soluble enzyme of the prolyl oligopeptidase family, which includes dipeptidyl peptidase 4 (DPP4). FAP is not generally expressed in normal adult tissues, but is found at high levels in activated myofibroblasts and hepatic stellate cells in fibrosis and in stromal fibroblasts of epithelial tumours. FAP possesses a rare catalytic activity, hydrolysis of the post‐proline bond two or more residues from the N‐terminus of target substrates. α 2 ‐antiplasmin is an important physiological substrate of FAP endopeptidase activity. This study reports the first natural substrates of FAP dipeptidyl peptidase activity. Neuropeptide Y, B‐type natriuretic peptide, substance P and peptide YY were the most efficiently hydrolysed substrates and the first hormone substrates of FAP to be identified. In addition, FAP slowly hydrolysed other hormone peptides, such as the incretins glucagon‐like peptide‐1 and glucose‐dependent insulinotropic peptide, which are efficient DPP4 substrates. FAP showed negligible or no hydrolysis of eight chemokines that are readily hydrolysed by DPP4. This novel identification of FAP substrates furthers our understanding of this unique protease by indicating potential roles in cardiac function and neurobiology. Structured digital abstract FAP cleaves GLP‐1‐amide by protease assay (View interaction) DPP4 cleaves PACAP by protease assay (View interaction) FAP cleaves PYY by protease assay (View interaction) FAP cleaves NPY by protease assay (View interaction) DPP4 cleaves Substance P by protease assay (View interaction) DPP4 cleaves GIP by protease assay (View interaction) DPP4 cleaves CCL11‐Eotaxin by protease assay (View interaction) DPP4 cleaves GLP‐1‐amide by protease assay (View interaction) DPP4 cleaves CXCL12‐SDF1 by protease assay (View interaction) FAP cleaves GRF by protease assay (View interaction) FAP cleaves GLP‐2 by <jats:ext-link xmlns:xlink="