Fibroblast activating protein α Also known as seprase protein or melanoma membrane binding gelatinase, a protein with a molecular weight of 170kDa encoded by the FAP gene (2q23) in the human body is a homodimer belonging to the serine protease family of membrane gelatinases. Selective expression is observed in the reactive matrix of epithelial cancer fibroblasts, granulation tissue of wound healing, and malignant cells of bone and soft tissue sarcomas. This protein is believed to be related to fibroblast growth during development, control of epithelial mesenchymal interactions, tissue repair, and epithelial carcinogenesis. FAP, also known as seprase, belongs to the SC protease family and is a subfamily of S9B proline oligopeptidases. Other members of the S9B subfamily include DPPIV, DPP8, and DPP9. FAP has a high correlation with DPPIV, with approximately 50% of the same amino acids. FAP is a dimer with catalytic activity of 170 kDa in size, and has both dipeptidase and gelatinase enzyme activities. Gelatinase activity requires the presence of glycine at the P2 position.