FAP (also known as seprase) is a single-pass type II membrane protein which belongs to thepeptidase S9B family. FAP appears to act as a proteolytically active 170-kDa dimer, consisting of two 97-kDa subunits. It is a member of the group type II integral serine proteases, which includes dipeptidyl peptidase IV ( DPPIV / CD26 ) and related type II transmembrane prolyl serine peptidases, which exert their mechanisms of action on the cell surface. FAP is also an endopeptidase that can degrade Gelatin, Collagens I and IV, Fibronectin, and Laminin as well as several peptide hormones. The enzymatic activity is dependent on FAP association with DPPIV on the cell surface. The matrix-dedgrading activity of FAP contributes to tumor cell migration and invasion. In addition, FAP can enhance tumor cell growth by limiting the development of anti-tumor immunity.
