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水稻的糠皮和胚经生理盐水浸取、离心后的上清液加热至８０℃处理１０ｍｉｎ，离心获得的上清液调ｐＨ至８．０，得到沉淀。沉淀溶解于０．０１ｍｏｌ／ＬＨＣｌ，经透析冷冻干燥得水稻巯基蛋白酶抑制剂（ＣＰＩ）粗品；粗品再经ＤＥＡＥ－Ｓｅｐｈａｒｏｓｅ柱线性离子梯度洗脱和ＳｅｐｈａｄｅｘＧ－１００柱分子筛层析，即可获得在ＰＡＧＥ、ＳＤＳ－ＰＡＧＥ和ＨＰＬＣ上均为单一蛋白带的ＣＰＩ样品。经上述步骤，ＣＰＩ可被纯化５８倍。经ＳｅｐｈａｄｅｘＧ－１００和ＳＤＳ－ＰＡＧＥ测定其分子量均为１２０００，Ｎ末端氨基酸为Ｐｒｏ，等电点５．６．水稻ＣＰＩ经１００℃处理１０ｍｉｎ后，其抑制活性无任何变化，在ｐＨ２．０～９．０之间，活性也不发生改变，但ｐＨ在９．０以上，其活性逐渐下降，水稻ＣＰＩ对木瓜蛋白酶是一种高亲和性的抑制剂，它对木瓜蛋白酶和无花果蛋白酶有强抑制作用，对菠萝蛋白酶仅有弱抑制作用，但对胰蛋白酶则全无抑制作用；其抑制类型属竞争性抑制剂类型，Ｋ＿ｉ值约３．５×１０￣（－８）ｍｏｌ／Ｌ对木瓜蛋白酶的抑制摩尔比约为１：１。
The rice bran and embryos were leached by physiological saline, and the supernatant after centrifugation was heated to 80 ° C for 10 min. The supernatant obtained by centrifugation was adjusted to pH 8.0 to obtain a precipitate. The precipitate was dissolved in 0.01mol / LHCl and lyophilized to obtain the crude product of crude thiol protease inhibitor (CPI) by dialysis. The crude product was subjected to linear ion-elution on a DEAE-Sepharose column and then to a SephadexG-100 column for molecular sieve chromatography. , A single protein band on both SDS-PAGE and HPLC. After these steps, CPI can be purified 58 times. Its molecular weight was 12000 by SephadexG-100 and SDS-PAGE, the N-terminal amino acid was Pro and the isoelectric point was 5.6. After the rice plants were treated with 100 ℃ for 10min, their inhibitory activities did not change, and their activities did not change between pH 2.0 and 9.0. However, the activities of rice CPI decreased gradually when the CPI was above 9.0. Protease is a high-affinity inhibitor, which has a strong inhibitory effect on papain and fig protease, only weak inhibition of bromelain, but no inhibition of trypsin; its inhibition type is a competitive inhibition Agent type, K_i value of about 3.5 × 10 ~ (-8) mol / L of papain inhibition molar ratio of about 1: 1.