Jowsey Ian R, Thomson Rachel E, Orton Terry C, Elcombe Clifford R, Hayes John D
Biomedical Research Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK.
Biochem J. 2003 Jul 15;373(Pt 2):559-69. doi: 10.1042/BJ20030415.
The class Kappa family of glutathione S-transferases (GSTs) currently comprises a single rat subunit (rGSTK1), originally isolated from the matrix of liver mitochondria [Harris, Meyer, Coles and Ketterer (1991) Biochem. J. 278, 137-141; Pemble, Wardle and Taylor (1996) Biochem. J. 319, 749-754]. In the present study, an expressed sequence tag (EST) clone has been identified which encodes a mouse class Kappa GST (designated mGSTK1). The EST clone contains an open reading frame of 678 bp, encoding a protein composed of 226 amino acid residues with 86% sequence identity with the rGSTK1 polypeptide. The mGSTK1 and rGSTK1 proteins have been heterologously expressed in Escherichia coli and purified by affinity chromatography. Both mouse and rat transferases were found to exhibit GSH-conjugating and GSH-peroxidase activities towards model substrates. Analysis of expression levels in a range of mouse and rat tissues revealed that the mRNA encoding these enzymes is expressed predominantly in heart, kidney, liver and skeletal muscle. Although other soluble GST isoenzymes are believed to reside primarily within the cytosol, subcellular fractionation of mouse liver demonstrates that this novel murine class Kappa GST is associated with mitochondrial fractions. Through the use of bioinformatics, the genes encoding the mouse and rat class Kappa GSTs have been identified. Both genes comprise eight exons, the protein coding region of which spans approx. 4.3 kb and 4.1 kb of DNA for mGSTK1 and rGSTK1 respectively. This conservation in primary structure, catalytic properties, tissue-specific expression, subcellular localization and gene structure between mouse and rat class Kappa GSTs indicates that they perform similar physiological functions. Furthermore, the association of these enzymes with mitochondrial fractions is consistent with them performing a specific conserved biological role within this organelle.
谷胱甘肽S-转移酶（GSTs）的Kappa家族目前仅包含一个大鼠亚基（rGSTK1），最初是从肝线粒体基质中分离得到的[哈里斯、迈耶、科尔斯和凯特勒（1991年）《生物化学杂志》278卷，第137 - 141页；彭布尔、沃德尔和泰勒（1996年）《生物化学杂志》319卷，第749 - 754页]。在本研究中，已鉴定出一个表达序列标签（EST）克隆，其编码一种小鼠Kappa类GST（命名为mGSTK1）。该EST克隆包含一个678 bp的开放阅读框，编码一种由226个氨基酸残基组成的蛋白质，与rGSTK1多肽的序列同一性为86%。mGSTK1和rGSTK1蛋白已在大肠杆菌中进行异源表达，并通过亲和层析进行纯化。发现小鼠和大鼠转移酶对模型底物均表现出谷胱甘肽结合和谷胱甘肽过氧化物酶活性。对一系列小鼠和大鼠组织中表达水平的分析表明，编码这些酶的mRNA主要在心脏、肾脏、肝脏和骨骼肌中表达。尽管其他可溶性GST同工酶被认为主要存在于细胞质中，但对小鼠肝脏进行亚细胞分级分离表明，这种新型小鼠Kappa类GST与线粒体部分相关。通过生物信息学的应用，已鉴定出编码小鼠和大鼠Kappa类GST的基因。这两个基因均由八个外显子组成，其蛋白质编码区域分别跨越mGSTK1约4.3 kb和rGSTK1约4.1 kb的DNA。小鼠和大鼠Kappa类GST在一级结构、催化特性、组织特异性表达、亚细胞定位和基因结构上的这种保守性表明它们执行相似的生理功能。此外，这些酶与线粒体部分的关联与它们在该细胞器内执行特定的保守生物学作用是一致的。
