Amajor trypsin inhibitor was purified from the extract of the whole grain of foxtail millet, Setaria italica, to an electrophoretically homogeneous protein by conventional methods. This inhibitor (FMTI-II) has a molecular weight of 7500 and contains high levels of basic amino acids, acidic amino acids, proline, and half-cystine. FMTI-II inhibited bovine and hog trypsins in a 1 : 1 (m/m) stoichiometry: the K{ values were 3.0 x 10~1l mand 2.2 x 10~10 m, respectively. Bovine a-chymotrypsin, subtilisin BPN', hog pepsin, and papain were not inhibited. The inhibitor was stable in a wide range of pH and was heatresistant at acidic pH. The chemical modification suggested that FMTI-II had a Lys-X bond as a trypsin reactive-site. FMTI-II resembles rice bran and wheat germ trypsin inhibitors, showing that it is a Bowman-Birk type inhibitor. Proteins with the ability to inhibit proteinases are widely distributed among cereal grains including barley, rye, wheat, corn, sorgham, oats, and rice, and a number of proteinase inhibitors have been purified and characterized.^These inhibitors are probably important physiologically and some inhibitors may have nutritional significance. They also serve as excellent models for the research on protein-protein interaction. Furthermore, the comparison of inhibitors from various cereals may contain information on the evolution of cereal proteins.

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