Biochemical and physiological characterization of a tau class glutathione transferase from rice (Oryza sativa)
Biochemical and physiological characterization of a tau class glutathione transferase from rice (Oryza sativa)
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水稻 (Oryza sativa) tau 类谷胱甘肽转移酶的生化和生理学特征
DOI：
10.1016/j.plaphy.2009.07.003
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发表时间：
2009-11-01
影响因子：
6.5
通讯作者：
Zeng, Qing-Yin
中科院分区：
文献类型：
--
作者：
Yang, Xue;Sun, Wu;Zeng, Qing-Yin
经典的II相解毒谷胱甘肽转移酶（GST）是催化谷胱甘肽与各种亲电化合物缀合的关键代谢酶。从水稻中克隆了一个tau类GST基因（OsGSTU 17），编码223个氨基酸，分子量为25.18 kDa。重组OsGSTU 17形成同源二聚体蛋白，并与各种外源性物质显示GSH缀合活性。以NBD-Cl为底物的动力学分析表明，每毫克蛋白质的Km为0.324 mM，V-max为0.219 μ mol/min。该酶有一个最大的活性在pH值为7.5，和一个高的热稳定性，其初始活性的81%，在55摄氏度为15分钟。定点诱变显示，Ser 15在N-末端结构域是一个关键的催化残基，负责稳定的巯基阴离子的酶结合谷胱甘肽。OsGSTU 17 mRNA在水稻地上部和地下部的不同组织中均有表达。OsGSTU 17 mRNA在不同组织中的相对转录水平在CDNB、过氧化氢和阿特拉津处理下差异显著，表明该基因在非生物胁迫下具有不同的调控机制。(C)2009年Elsevier Masson SAS。All rights reserved.
The classical phase II detoxification glutathione transferases (GSTs) are key metabolic enzymes that catalyze the conjugation of glutathione to various electrophilic compounds. A tau class GST gene (OsGSTU17) was cloned from rice, which encodes a protein of 223 amino acid residues with a calculated molecular mass of 25.18 kDa. The recombinant OsGSTU17 formed a homodimer protein and showed GSH-conjugating activity with various xenobiotics. Kinetic analysis with respect to NBD-Cl as substrate revealed a K-m of 0.324 mM and V-max of 0.219 mu mol/min per mg of protein. The enzyme had a maximum activity at pH 7.5, and a high thermal stability with 81% of its initial activity at 55 degrees C for 15 min. Site-directed mutagenesis revealed that Ser15 in the N-terminal domain is a critical catalytic residue, responsible for stabilisation of the thiolate anion of enzyme-bound glutathione. OsGSTU17 mRNA was expressed in different tissues of rice, both above and below ground. The relative transcript levels of OsGSTU17 mRNA varied significantly among the tissues in response to CDNB, hydrogen peroxide and atrazine treatments, indicating the gene has diverse regulation mechanisms in response to abiotic stresses. (C) 2009 Elsevier Masson SAS. All rights reserved.