百合巯基蛋白酶抑制剂的纯化及部分性质研究

Purification and Characterization of a Lily Cysteine Proteinase Inhibitor

百合的鳞茎中含有一种对木瓜蛋白酶有强抑制作用的巯基蛋白酶抑制剂．百合的鳞茎经浸取加热处理，木瓜蛋白酶偶联的Ｓｅｐｈａｒｏｓｅ４Ｂ柱亲和层析和ＳｅｐｈａｄｅｘＧ－１００分子筛层析，可获得在ＰＡＧＥ和ＳＤＳ－ＰＡＧＥ均为单一蛋白带的百合巯基蛋白酶抑制剂（ＣＰＩ）．此ＣＰＩ为单链蛋白，含有０．３０７％的中性糖；Ｎ端氨基酸为Ｉｌｅ；ＳＤＳ－ＰＡＧＥ测得亚基分子量为１２０００；ＳｅｐｈａｄｅｘＧ－１００测得分子量为１２５００．百合ＣＰＩ在１００℃内和ｐＨ２～１２范围内非常稳定；对木瓜蛋白酶的抑制属竞争性抑制类型，其Ｋｉ值为１．１５×１０^（－９）ｍｏｌ／Ｌ，对木瓜蛋白酶的抑制摩尔比为８．５：１．

A cysteine proteinase inhibitor (CPI) that inhibited the activity of papain (E. C. 3. 4.22. 2) was found in the bulb of lily. This CPI was purified by a series of procedures including extraction. heating, papain-Sepharose 4B affinity chromagraphy, and gel filtration on Sephadex G-100. The purified lily inhibitor was a single polypeptide with a molecular weight 12 000 in SDS-PAGE and 12 500 in gel filtration. The lily CPI was very stable below 100℃ and between PH2─12. It contained 0. 307% neutral sugar,with Ile as the N-terminal amino acid. The inhibition of papain by lily CPI was competitive,with a K_1 value of 1. 1 5 ×10￣(-9) mol/L and the mole ratio was 8. 5: 1.