作　　者： ; ; ;

机构地区： 中山大学生命科学学院

出　　处： 《植物生理学报（0257-4829)》 2001年第5期425-430,共6页

摘　　要： 从 6d苗龄的豇豆幼苗初生叶中提纯得到的多胺氧化酶是一种糖蛋白 ,其碳水化合物含量为8.1 7%。全酶分子量约为 1 46kD ,由分子量为 70kD的两个相同亚基组成 ,每个亚基含 1个Cu2 +。该酶的等电点为 6.2 ,吸收光谱分别在波长 2 78nm和 5 0 0nm处有 1吸收峰。 8种蛋白质修饰剂修饰试验并配合底物保护证实酪氨酸、赖氨酸和色氨酸残基及 SH都不是该酶活性中心的必需基团 ,而组氨酸残基则是活性中心的必需基团。进一步分析部分失活的修饰酶动力学参数的变化得知 。 Partial structural characteristics and essential groups in the active center of a polyamine oxidase (EC1.4.3.6) purified from the primary leaves of 6 day old cowpea ( Vigna unguiculata L.) were studied. The enzyme was a glycoprotein with a carbohydrate content of 8.17%. Its apparent M r estimated by Sepharose Cl 4B gel filtration was about 146 kD, and SDS PAGE gave a single protein band corresponding to a M r of 70 kD. These results indicate that the enzyme is a dimer of identical subunits. The enzyme contained two Cu 2+ ions per molecule in its native state,and its isoelectric point was about 6.2 determined by isoelectric focusing with the Rotofor System (Bio Rad). The absorption spectrum of the enzyme showed a well defined peak at 278 nm and a small peak at 500 nm. The chemical modification studies with p chloromercuribenzoate, 2,2′ dinitro 5,5′ dithiodibenzoic acid, N acetylimidazole, p nitrobenzenesulfonyl fluoride, trinitrobenzenesulfonic acid, N bromosuccinimide, iodoacetamide and diethylpyrocarbonate (DEPC) showed that histidine residues were involved in the active sites and thiol groups, tyrosyl residues, lysyl residues and tryptophyl residues were non essential to the catalytic activity of the enzyme. The kinetic parameters of the enzyme partially inactivated by DEPC, imply that histidine residues might be the catalytic site of the enzyme.

关 键 词： 豇豆 多胺氧化酶 化学修饰 活性中心 初生叶

领　　域： [生物学]