Protein Domain : Proteinase inhibitor A/B IPR016308

Type	Family
Description	This small family of proteins from plants includes proteinase inhibitors A and B from Sagittaria sagittifolia (Arrowhead) and a trypsin/chymotrypsin inhibitor from Alocasia macrorrhizos (Giant taro) [ ]. They belong to the MEROPS inhibitor family I3, clan IC. The arrowhead proteinase inhibitor A and B (APIA and APIB) are double-headed and multifunctional, consisting of 179 amino acid residues with three disulphide bridges. The reactive site residues Lys(44), Arg(76) and Arg(87) of APIB are predicted by sequence comparison to other proteinase inhibitors [ ]. The two previously predicted reactive site residues, Lys-44 and Arg-76 of inhibitor B, were confirmed by site-directed mutagenesis. The two predicted active sites of APIA, namely, Ser-82 and Leu-87, leu and Arg in APIB respectively, were substituted by these two corresponding residues, which confirmed their importance as active site residues [].
Short Name	Prot_inh_API-A/B