Function: Serine protease inhibitor. The major targets of this inhibitor are plasmin and trypsin, but it also inactivates matriptase-3/TMPRSS7 and chymotrypsin.
Subunit: Forms protease inhibiting heterodimer with TMPRSS7.
Subcellular Location: Secreted.
Tissue Specificity: Expressed by the liver and secreted in plasma.