Competitively inhibits Glu S.griseus protease by forming probably a 1:1 complex. BGIA has no inhibitory activity against 2 other acidic amino acid-specific endopeptidases (S.aureus protease V8 and B.subtilis proteinase), chymotrypsin, trypsin, pancreatic elastase, and papain, although subtilisin Carlsberg was strongly inhibited. Belongs to the protease inhibitor I13 (potato type I serine protease inhibitor) family.