Rouleau M, Lamy F
Can J Biochem. 1975 Sep;53(9):958-74. doi: 10.1139/o75-133.
A trypsin inhibitor isolated from a potato acetone powder has been purified by affinity chromatography. This protein inhibits trypsin mole per mole. To a lesser extent it combines also with chymotrypsin and elastase. For trypsin, K1 = 8 X 10(-7) M. The inhibitor has a single polypeptide chain of 207 amino acid residues. It contains no sugar or free sulfhydryl groups. Its extinction coefficient E2801% = 10.3 and its isoelectric point is 6.9. Its molecular weight is of the order of 21 000-22000, as determined by sedimentation equilbrium, by inhibition experiment or from its amino acid composition. These same techniques, taken together with the single band observed at different pH on polyacrylamide gel electrophoresis, indicate that the protein purified is monodisperse. However, the finding of two N-terminal amino acid residues, leucine and aspartic acid, and the different stoichometry observed during the interaction of the inhibitor, either with trypsin or with chymotrypsin and elastase, raises the possibility that our preparation is contaminated by a polyvalent inhibitor not detectable by physiochemical methods.
从马铃薯丙酮粉中分离出的一种胰蛋白酶抑制剂已通过亲和层析法进行了纯化。这种蛋白质以每摩尔抑制一摩尔胰蛋白酶。它在较小程度上也能与胰凝乳蛋白酶和弹性蛋白酶结合。对于胰蛋白酶，K1 = 8×10⁻⁷ M。该抑制剂具有一条由207个氨基酸残基组成的单多肽链。它不含糖或游离巯基。其消光系数E2801% = 10.3，等电点为6.9。通过沉降平衡、抑制实验或根据其氨基酸组成测定，其分子量约为21000 - 22000。这些相同的技术，再加上在聚丙烯酰胺凝胶电泳上不同pH条件下观察到的单一条带，表明纯化得到的蛋白质是单分散的。然而，发现有两个N端氨基酸残基，即亮氨酸和天冬氨酸，以及在抑制剂与胰蛋白酶、胰凝乳蛋白酶或弹性蛋白酶相互作用过程中观察到的不同化学计量关系，增加了我们的制剂被一种用物理化学方法检测不到的多价抑制剂污染的可能性。
