HGFA Inhibitor 1 is an endogenous inhibitor of the kunitz-type serine proteinase HGF-activator (HGFA). HGF was first described as a hepatocyte-specific mitogen and survival factor, and has since been shown to exert a variety of actions on many cell types by binding to its MET receptor. HGF is activated by cleavage of the single-chain form to form a two-chain version by HGFA. HGFA Inhibitor 1 also inhibits trypsin, and MTSP-1 (Matriptase), a serine proteinase that also activates HGF. HGFB Inhibitor 1 is a splice variant of HGFA Inhibitor 1, and contains a 16 amino acid insert after the first kringle domain, relative to the HGFA Inhibitor 1 sequence.
