Laboratories of The Rockefeller Institute for Medical Research, Princeton, New Jersey.
J Gen Physiol. 1947 Mar 20;30(4):291-310. doi: 10.1085/jgp.30.4.291.
A study has been made of the general properties of crystalline soybean trypsin inhibitor. The soy inhibitor is a stable protein of the globulin type of a molecular weight of about 24,000. Its isoelectric point is at pH 4.5. It inhibits the proteolytic action approximately of an equal weight of crystalline trypsin by combining with trypsin to form a stable compound. Chymotrypsin is only slightly inhibited by soy inhibitor. The reaction between chymotrypsin and the soy inhibitor consists in the formation of a reversibly dissociable compound. The inhibitor has no effect on pepsin. The inhibiting action of the soybean inhibitor is associated with the native state of the protein molecule. Denaturation of the soy protein by heat or acid or alkali brings about a proportional decrease in its inhibiting action on trypsin. Reversal of denaturation results in a proportional gain in the inhibiting activity. Crystalline soy protein when denatured is readily digestible by pepsin, and less readily by chymotrypsin and by trypsin. Methods are given for measuring trypsin and inhibitor activity and also protein concentration with the aid of spectrophotometric density measurements at 280 mmicro.
已对结晶大豆胰蛋白酶抑制剂的一般性质进行了研究。大豆抑制剂是球蛋白型的稳定蛋白质，分子量约为 24000。其等电点在 pH4.5。它通过与胰蛋白酶结合形成稳定的化合物来抑制约等量的结晶胰蛋白酶的蛋白水解作用。糜蛋白酶仅被大豆抑制剂轻微抑制。胰蛋白酶和大豆抑制剂之间的反应在于形成可逆转离解的化合物。抑制剂对胃蛋白酶没有影响。大豆抑制剂的抑制作用与蛋白质分子的天然状态有关。通过热、酸或碱使大豆蛋白变性会导致其对胰蛋白酶抑制作用呈比例下降。变性的逆转导致抑制活性呈比例增加。结晶大豆蛋白变性后，容易被胃蛋白酶消化，而较不易被糜蛋白酶和胰蛋白酶消化。文中提供了使用 280nm 分光光度密度测量法测量胰蛋白酶和抑制剂活性以及蛋白质浓度的方法。
