Joubert F J, Merrifield E H, Dowdle E B
Int J Biochem. 1987;19(7):601-6. doi: 10.1016/0020-711x(87)90225-4.
Although the Kunitz-type proteinase inhibitors from the seeds of various Erythrina species have similar molecular weights (approximately 20,000), and share many other chemical characteristics, they could nevertheless be divided into three groups on the basis of their relative abilities to inhibit chymotrypsin, trypsin and tissue plasminogen activator. Group a inhibitors were relatively specific for chymotrypsin; they were poor inhibitors of trypsin and had no apparent effect upon tissue plasminogen activator. Group b proteins inhibited trypsin strongly and chymotrypsin slightly less effectively. They had no effect upon t-PA. Group c inhibitors inhibited trypsin, chymotrypsin and t-PA. Analysis of the amino acid composition of the three groups of inhibitors revealed major differences in alanine content. Minor differences in the content of most other amino acids were also noticed. Group b and group c inhibitors had, in most cases, the same reactive sites (Arg-Ser). The sequences neighbouring the reactive sites showed a significant degree of homology. Chemical modification of arginine in proteinase inhibitors from the seeds of E. latissima and soybeans using 1-2-cyclohexanedione confirmed the presence or absence of arginine in the reactive sites.
尽管来自各种刺桐属植物种子的库尼茨型蛋白酶抑制剂具有相似的分子量（约20,000），并具有许多其他化学特性，但根据它们抑制胰凝乳蛋白酶、胰蛋白酶和组织纤溶酶原激活剂的相对能力，仍可分为三组。a组抑制剂对胰凝乳蛋白酶具有相对特异性；它们对胰蛋白酶的抑制作用较弱，对组织纤溶酶原激活剂没有明显影响。b组蛋白强烈抑制胰蛋白酶，对胰凝乳蛋白酶的抑制作用稍弱。它们对组织纤溶酶原激活剂没有影响。c组抑制剂抑制胰蛋白酶、胰凝乳蛋白酶和组织纤溶酶原激活剂。对这三组抑制剂的氨基酸组成分析表明，丙氨酸含量存在主要差异。在大多数其他氨基酸的含量上也发现了微小差异。在大多数情况下，b组和c组抑制剂具有相同的活性位点（精氨酸-丝氨酸）。活性位点附近的序列显示出高度的同源性。使用1,2-环己二酮对刺桐和大豆种子中的蛋白酶抑制剂中的精氨酸进行化学修饰，证实了活性位点中精氨酸的存在与否。
