Zhou Xing-Ding, Jin Yang, Lu Qiu-Min, Li Dong-Sheng, Zhu Shao-Wen, Wang Wan-Yu, Xiong Yu-Liang
Department of Toxinology, Kunming Institute of Zoology, The Chinese Academy of Sciences, 650223 Kunming, Yunnan, PR China.
Comp Biochem Physiol B Biochem Mol Biol. 2004 Feb;137(2):219-24. doi: 10.1016/j.cbpc.2003.11.007.
A chymotrypsin inhibitor, designated NA-CI, was isolated from the venom of the Chinese cobra Naja atra by three-step chromatography. It inhibited bovine alpha-chymotrypsin with a Ki of 25 nM. The molecular mass of NA-CI was determined to be 6403.8 Da by matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) analysis. The complete amino acid sequence was determined after digestion of S-carboxymethylated inhibitor with Staphylococcus aureus V8 protease and porcine trypsin. NA-CI was a single polypeptide chain composed of 57 amino acid residues. The main contact site with the protease (P1) has a Phe, showing the specificity of the inhibitor. NA-CI shared great similarity with the chymotrypsin inhibitor from Naja naja venom (identities=89.5%) and other snake venom protease inhibitors.
一种名为NA - CI的胰凝乳蛋白酶抑制剂通过三步色谱法从中华眼镜蛇（Naja atra）的毒液中分离出来。它对牛α-胰凝乳蛋白酶具有抑制作用，抑制常数Ki为25 nM。通过基质辅助激光解吸电离飞行时间（MALDI - TOF）分析，NA - CI的分子量测定为6403.8 Da。在用金黄色葡萄球菌V8蛋白酶和猪胰蛋白酶消化S - 羧甲基化抑制剂后，确定了其完整的氨基酸序列。NA - CI是由57个氨基酸残基组成的单条多肽链。与蛋白酶的主要接触位点（P1）含有苯丙氨酸，显示出该抑制剂的特异性。NA - CI与眼镜蛇（Naja naja）毒液中的胰凝乳蛋白酶抑制剂（同一性 = 89.5%）以及其他蛇毒蛋白酶抑制剂具有高度相似性。
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