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豇豆初生叶多胺氧化酶的分子特性

何生根, 黄学林, 傅家瑞

中山大学生命科学学院.广东,广州 510275

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8.17%。全酶分子量约为146kD,由分子量为70kD的两个相同亚基组成,每个亚基含1个Cu~(2+)。该酶的等电点为6.2,吸收光谱分别在波长278nm和500nm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,组氨酸残基可能处于酶分子的催化部位而非底物的结合部位。

关键词： 豇豆; 多胺氧化酶; 化学修饰; 活性中心

Molecular properties of polyamine oxidase from cowpea primary leaves

He Shenggen, Huang Xuelin, Fu Jiarui

The School of Life Sciences,Zhongshan University.Guangzhou 510275,Guangdong

Abstract

The enpolyamine oxidase 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.

Key words: Cowpea;Polyamine oxidase;Chemical modification;Active center

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引用本文：

何生根, 黄学林, 傅家瑞. 豇豆初生叶多胺氧化酶的分子特性[J]. 生理学报 2001; 53 (5): .

He Shenggen, Huang Xuelin, Fu Jiarui. Molecular properties of polyamine oxidase from cowpea primary leaves. Acta Physiol Sin 2001; 53 (5): (in Chinese with English abstract).