Purification, partial characterization, and immunological relationships of multiple low molecular weight protease inhibitors of soybean.
Five protease inhibitors, I--V, in the molecular weight range 7000--8000 were purified from Tracy soybeans by ammonium sulfate precipitation, gel filtration on Sephadex G-100 and G-75, and column chromatography on DEAE-cellulose. In common with previously described trypsin inhibitors from legumes, I--V have a high content of half-cystine and lack tryptophan. By contrast with other legume inhibitors, inhibitor II contains 3 methionine residues. Isoelectric points range from 6.2 to 4.2 in order from inhibitor I to V. Molar ratios (inhibitor/enzyme) for 50% trypsin inhibition are I = 4.76, II = 1.32, III = 3.22, IV = 2.17, V = 0.97. Only V inhibit chymotrypsin significantly (molar ratio = 1.33 for 50% inhibition). The sequence of the first 16 N-terminal amino acid residued of inhibitor V is identical to that of the Bowman-Birk inhibitor; all other observations also indicate that  inhibitor V and Bowman-Birk are identical. The first 20 N-terminal amino acid residues of inhibitor II show high homology to those of Bowman-Birk inhibitor, differing by 1 deletion and 5 substitutions. Immunological tests show that inhibitors I through IV are fully cross-reactive with each other but are distinct from inhibitor V.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002241:Carbohydrates / Q000032:analysis; D003429:Cross Reactions; D000939:Epitopes; D008970:Molecular Weight; D010944:Plants / Q000032:analysis; D011233:Precipitin Tests; D011863:Radioimmunoassay; D013025:Glycine max; D014360:Trypsin Inhibitor, Kunitz Soybean / Q000276:immunology / Q000302:isolation & purification; D014361:Trypsin Inhibitors / Q000302:isolation & purification
D000596:Amino Acids; D002241:Carbohydrates; D000939:Epitopes; D014361:Trypsin Inhibitors; D014360:Trypsin Inhibitor, Kunitz Soybean