Abstract
A major 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, prolinc, and half-cystine. FMTI-II inhibited bovine and hog trypsins in a 1:1 (M/M) stoichiometry: the Ki values were 3.0 × 10-11 M and 2.2 × 10-10 M, respectively. Bovine α-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.
