The bowman-birk inhibitor (BBI)family of proteins dual function proteinase inhibitors found in plants and in particular in the seeds of legumes, as well as in cereal grains (Birk, Chemical Biology and Drug Design) .that inhibit both trypsin and chymotrypsin (Rawlings et al. Biochemistry Journal, Laskowski and Kato, Annu. Rev. Biochem). Members of this family have an apparent duplicated structure and possess two distinct inhibitory sites. These inhibitors are primarily In cereals, they exist in two forms, one of which is a duplication of the basic structure (Tashiro et al. J. Biochem).Proteins of the Bowman–Birk inhibitor family of serine proteinase inhibitors directly interact with the enzymes they inhibit creating a one to one complex via an exposed surface loop that adopts the canonical proteinase inhibitory conformation resulting in a noncovalent complex that renders the proteinase inactive.