Odani S, Koide T, Ono T
J Biol Chem. 1983 Jul 10;258(13):7998-8003.
The amino acid sequence of barley trypsin inhibitor has been determined. The protein is a single polypeptide consisting of 121 amino acid residues and has Mr = 13,305. No free sulfhydryl groups were detected by Ellman's reagent, which indicates the presence of five disulfide bridges in the molecule. The primary site of interaction with trypsin was tentatively assigned to the arginyl-leucyl residues at positions 33 and 34. On comparison of the sequence of this inhibitor with those of other proteinase inhibitors, we found that the barley trypsin inhibitor could not be classified into any of the established families of proteinase inhibitors (Laskowski, M., Jr., and Kato, I. (1980) Annu. Rev. Biochem. 49, 593-626) and that this inhibitor should represent a new inhibitor family. On the other hand, this trypsin inhibitor showed a considerable similarity to wheat alpha-amylase inhibitor (Kashlan, N., and Richardson, M. (1981) Phytochemistry (Oxf.) 20, 1781-1784) throughout the whole sequence, suggesting a common ancestry for both proteins. This is the first case of a possible evolutionary relationship between two inhibitors directed to totally different enzymes, a proteinase and a glycosidase.
大麦胰蛋白酶抑制剂的氨基酸序列已被确定。该蛋白质是由121个氨基酸残基组成的单条多肽链，相对分子质量为13305。用埃尔曼试剂未检测到游离巯基，这表明该分子中存在5个二硫键。与胰蛋白酶相互作用的主要位点初步确定为第33和34位的精氨酰 - 亮氨酰残基。将该抑制剂的序列与其他蛋白酶抑制剂的序列进行比较时，我们发现大麦胰蛋白酶抑制剂不能归入任何已确立的蛋白酶抑制剂家族（拉斯科夫斯基，M.，Jr.，和加藤，I.（1980年）《生物化学年度评论》49，593 - 626），并且该抑制剂应代表一个新的抑制剂家族。另一方面，这种胰蛋白酶抑制剂在整个序列上与小麦α -淀粉酶抑制剂（卡什兰，N.，和理查森，M.（1981年）《植物化学》（牛津）20，1781 - 1784）有相当大的相似性，这表明这两种蛋白质有共同的祖先。这是针对两种完全不同的酶（一种蛋白酶和一种糖苷酶）的两种抑制剂之间可能存在进化关系的首例。
