Inhibits trypsin in vitro. Probably plays a protective role through inhibition of insect midgut proteases. Expressed in the developing endosperm. Not detected in embryo, aleurone, coleoptile, roots and leaves. Five disulfide bonds are present (Probable), which are essential for the inhibitor activity. The sequence heterogeneity suggests that more than one gene exists for this inhibitor. The genes may be alleles, or multiple loci could exist. Belongs to the protease inhibitor I6 (cereal trypsin/alpha-amylase inhibitor) family. Truncated C-terminus.