水生动物谷胱甘肽硫转移酶研究进展

谷胱甘肽硫转移酶(gluthione S-transferase,GST)是一种广泛存在于各种生物组织中的小分子水溶性蛋白.GST属于Ⅱ相代谢酶,主要功能是催化某些内源性或外来有害物质的亲电子基团与还原型谷胱甘肽的巯基结合,增加其疏水性使其易于排出体外,同时某些GST还具有谷胱甘肽过氧化酶活性.本文着重介绍了近年来国内外对水生动物GST的基础研究包括组织分布、同工酶类型和结构基因研究,以及各种环境污染物对水生动物GST的影响,探讨其作为生物标志物的可行性.     

水生动物谷胱甘肽硫转移酶研究进展

谷胱甘肽硫转移酶（gluthione S-transferase，GST）是一种广泛存在于各种生物组织中的小分子水溶性蛋白．GST属于Ⅱ相代谢酶．主要功能是催化某些内源性或外来有害物质的亲电子基团与还原型谷胱甘肽的巯基结合，增加其疏水性使其易于排出体外，同时某些GST还具有谷胱甘肽过氧化酶活性．本文着重介绍了近年来国内外对水生动物GST的基础研究包括组织分布、同工酶类型和结构基因研究．以及各种环境污染物对水生动物GST的影响，探讨其作为生物标志物的可行性．     

三丁基锡对翡翠贻贝谷胱甘肽硫转移酶活性的影响

在实验条件下,将翡翠贻贝分别暴露于1,10,100,1 000 ng/L的三丁基锡溶液中,1,4,7,14,21 d后取样,测定鳃和消化腺谷胱甘肽硫转移酶(Glutathione S-transferase,GST)同工酶的活性(GSTs,GST-μ,GST-π).结果表明:(1)生理条件下GST同工酶在鳃组织中分布高于消化腺,且活性大小为:GSTs >GST-π>GST-μ;(2)污染条件下,各GST同工酶活性随暴露时间的变化趋势各有不同.鳃和消化腺GSTs活性在暴露第1天被强烈诱导,而后逐步表现为抑制作用;鳃GST-π活性基本无显著变化,消化腺GST-π活性于第7天被诱导至高点,并逐渐恢复到对照水平或被抑制;消化腺GST-μ活性随着污染时间的延长整体受到抑制.     

谷胱甘肽硫转移酶在东亚飞蝗两个种群mRNA的表达研究

为研究东亚飞蝗谷胱甘肽硫转移酶基因(GSTs)表达与代谢能力的相关性,应用实时荧光定量PCR技术,对东亚飞蝗沧州和天津种群9个谷胱甘肽硫转移酶基因的mRNA表达情况进行了研究.结果表明:9个GSTs基因在东亚飞蝗不同发育阶段具有表达差异,基因LmGST1、LmGST3、LmGST5、LmGST7和LmGST8随着蝗虫的生长发育表达量增高,这些基因可能影响虫体对有毒化学物质的敏感性.沧州种群GSTs的表达水平高于天津种群,据此推测沧州种群个体对有机磷农药的代谢解毒能力强,对杀虫剂的敏感性低.     

哺乳动物谷胱甘肽转移酶研究进展

谷胱甘肽转移酶(谷胱甘肽硫转移酶)(GSTs)是一类广泛分布于微生物、植物、昆虫、鱼以及哺乳动物,在诸多生物学过程中发挥重要作用的蛋白超家族,具有解毒和清除过氧化物双重功能.近年来,国内外研究人员进一步对GST在生物化学、结构生物学、分子生物学、进化生物学以及基因组学等层面进行了大量的分析和研究.本文将针对有关GST的研究展开综述,以期为深入开展哺乳动物GST基因适应和进化研究提供借鉴.     

废旧干电池污染液对泥鳅谷胱甘肽硫转移酶活性的影响

将泥鳅暴露于不同浓度的废旧干电池污染液中,于48小时、72小时测定其谷胱甘肽硫转移酶(GSTs)的活性,发现低浓度、短时间内GSTs活性被诱导,随着废旧干电池污染液浓度的增大和暴露时间的延长,GSTs活性被抑制。这些结果表明,GSTs可作为生物标志物来监测水生态系统的污染。     

GSTs,NATs基因多态性与癌症易感性

谷胱甘肽硫转移酶（GSTs)和N－乙酰转移酶（NATs)与异源物质（xenobiotics)与人类的代,激活,解毒等过程密切相关,由于编码这两类酶的基因呈高度鑫态性,因而在人数中GSTs和NATs的活性特征不尽相同,现有的研究指出：GSTs和NATs基因多态性在某些人群中与各类癌症的易感性相关,文章基于前人研究成果并结合我室的[研究进展就这方面的研究工作做了局部的综述。     

植物体内的多功能蛋白酶——谷胱甘肽转移酶

谷胱甘肽转移酶(Glutathione S-transferases,GSTs)在植物体内普遍存在,是由一个大的多基因家族编码的多功能蛋白酶。GSTs的表达受多种环境因子的诱导,在植物的生长发育、次生代谢和耐逆中有重要作用。本文简要介绍了GST的研究概况,重点讨论了其生理功能。     

植物谷胱甘肽转移酶和盐胁迫

谷胱甘肽转移酶 (GSTs)的种类不一 ,在植物异生代谢和内生代谢中都表现了一定的功能 ,通过转基因技术使之在植物体中过量表达显示它在植物耐盐过程中也起到了一定的作用 .     

植物的谷胱甘肽转移酶家族

植物的谷胱甘肽转移酶(Glutathione transferases,GSTs;EC 2.5.1.18)是一个大家族;根据蛋白同源性和基因组织结构,植物GST分为φ、ζ、τ、θ、λ五类;GST主要在胞液中表达,是由约26kDa亚基组成的同源二聚体或异源二聚体,形成疏水的50kDa的蛋白;在不同组织和不同的环境条件下,基因表达差异很大.GST在植物的初级代谢和二级代谢、胁迫耐受、细胞信号等方面行使功能.     

Squid major lens polypeptides are homologous to glutathione S-transferases subunits

The eye lenses of cephalopods and vertebrates evolved relatively recently and by independent routes. They provide a good experimental model for the study of convergent evolution at the protein level. One proposal is that pre-existing proteins were recruited as structural eye lens proteins during evolution. This has been confirmed for the vertebrate eye lens structural proteins, or crystallins, which have been intensively studied. Despite the limited information about cephalopod eye lenses, it has been suggested that glutathione S-transferases (GSTs) are a possible evolutionary ancestor of the squid major lens proteins. Recently, the N-terminal sequence of the squid major lens protein was shown to be 55% homologous with that of the Ya subunit of the rat GST. Here, we demonstrate that the squid major lens polypeptides are encoded by a gene family of at least three members. We characterize two cDNAs corresponding to these genes and show they probably either are GST subunits themselves, or share an evolutionary ancestor with them.     

Convergent evolution of similar function in two structurally divergent enzymes

An example of two related enzymes that catalyse similar reactions but possess different active sites is provided by comparing the structure of Escherichia coli thioredoxin reductase with glutathione reductase. Both are dimeric enzymes that catalyse the reduction of disulphides by pyridine nucleotides through an enzyme disulphide and a flavin. Human glutathione reductase contains four structural domains within each molecule: the flavin-adenine dinucleotide (FAD)- and nicotinamide-adenine dinucleotide phosphate (NADPH)-binding domains, the 'central' domain and the C-terminal domain that provides the dimer interface and part of the active site. Although both enzymes share the same catalytic mechanism and similar tertiary structures, their active sites do not resemble each other. We have determined the crystal structure of E. coli thioredoxin reductase at 2 A resolution, and show that thioredoxin reductase lacks the domain that provides the dimer interface in glutathione reductase, and forms a completely different dimeric structure. The catalytically active disulphides are located in different domains on opposite sides of the flavin ring system. This suggests that these enzymes diverged from an ancestral nucleotide-binding protein and acquired their disulphide reductase activities independently.     

Seasonal variation of gut Cyanophyta contents and liver GST expression of mud carp （Cirrhina molitorella） and Nile tilapia （Oreochromis niloticus） in the tropical Xiangang Reservoir （Huizhou, China）

Liver glutathione S-transferase(GST) plays a major role in the detoxification of microcystins(MCs) via conjugation to glutathione(GSH).We evaluated the relationship between seasonal variation in fish gut contents and the expression of GST isoforms in mud carp(Cirrhina molitorella) and Nile tilapia(Oreochromis niloticus).We quantified the abundance and diversity of plankton in the water column and foregut of mud carp and Nile tilapia in the tropical Xiangang Reservoir between October 2007 and July 2008.The mRNA expression of 7 liver GST isoforms was determined by real-time RT-PCR.The gut contents of both species were dependent on the amount and type of phytoplankton and zooplankton in the water.The expression of liver GST genes in Nile tilapia and mud carp was positively and negatively correlated,respectively,with the abundance of toxic cyanobacteria in the fore-gut.The expression of liver GST mRNA was correlated to the abundance of toxic cyanobacteria in the gut contents of both species,suggesting that mRNA expression of GST isoforms could be used as a biomarker in Nile tilapia and mud carp to monitor cyanobacteria blooms in reservoirs.     

葱蝇谷胱甘肽S - 转移酶基因的克隆与序列分析(动物科学)

谷胱苷肽S-转移酶(GST)是昆虫体内广泛存在的一类解毒酶,可以保护机体免受内源性或氧化物的损害。昆虫对一些杀虫剂的抗性与GST表达水平增高有关。GST的研究主要集中在杀虫剂抗性上,可将其作为昆虫的药物靶标,设计和开发新型的杀虫剂。采用RACE的方法,克隆了葱蝇(Delia antiqua)GST基因cDNA的全长序列(GenBank登录号:JQ625502),获得的cDNA全长874bp,其中阅读框ORF 627bp,编码208个氨基酸,推测其相对分子质量为23.9kD,等电点为5.83。通过该基因推导的氨基酸序列与其它物种的GST蛋白进行相似性比较和系统发育分析,发现葱蝇与丝光绿蝇(Lucilia cuprina)的谷胱甘肽转移酶氨基酸序列同源性最高。该结果进一步丰富了GST基因的基础数据,有助于葱蝇的杀虫剂抗性机理和发育机理的相关研究。     

吲哚丁酸对怀牛膝幼苗生长及谷胱甘肽抗氧化酶系统的影响

对怀牛膝幼苗施加不同浓度的吲哚丁酸(IBA),研究IBA对其幼苗生长及谷胱甘肽抗氧化酶系统的影响.结果显示:1.0mg/L IBA能同时显著提高怀牛膝叶片中谷胱甘肽过氧化物酶(GPx)、谷胱甘肽还原酶(GR)、谷胱甘肽S-转移酶(GST)的活性及蛋白质含量(P<0.05),并能促进其幼苗株高、根长和根干重的增加.结论:1.0mg/L IBA促进了牛膝幼苗的生长,提高了叶片中谷胱甘肽抗氧化酶系统的活性及蛋白质含量,有效的增强了植株的抗逆性.     

翡翠贻贝(Perna viridis)谷胱甘肽硫转移酶同工酶的分离纯化及部分性质研究

以翡翠贻贝（Perna viridis）消化腺为材料,经GST rap^TMFF柱亲和层析,分离纯化得到总谷胱甘肽硫转移酶。而后经DEAE离子交换层析得到三个洗脱峰M₁、M₂、M₃,分别占总蛋白含量的77%,16%,2.9%,对其进行SDS-PAGE分析,结果表明M₁可能是由分子量为25 kD的蛋白质亚基组成的同型二聚体,M₂、M₃可能为异型二聚体,M₂由25 kD和23kD两个亚基组成,M₃由27kD和23kD两个亚基组成。以1-氯-2,4-二硝基苯（CDNB）、3,4-二氯硝基苯（DCNB）、4-硝基氯化苄（NBC）、利尿酸（ETHA）4种底物对M₁、M₂、M₃进行动力学分析,发现M₁、M₂、M₃分别对ETHA、DCNB、NBC亲和力更好,Km分别为1.08mmol/L、1.51 mmol/L、0.89mmol/L,Vmax分别为54.9μmol/min/mg,40.3μmol/min/mg,19.4μmol/min/mg。     

Rat liver protein linking chemical and immunological detoxification systems.

Mammals have separate enzymatic and cellularly mediated detoxification systems. Glutathione S-transferases (GSTs) protect against xenobiotic chemicals which continuously enter the body, largely through mucous membranes. These enzymes catalyse the conjugation of glutathione with a wide variety of electrophilic compounds rendering them non-toxic. Mammals also mount a cellular immunological response on entry of foreign cells, viruses or macromolecules into the body. T lymphocytes mobilize at the site of foreign body entry and secrete protein messengers called lymphokines. Secondary to T lymphocytes, macrophages concentrate at the infection site and function in antigen processing and phagocytosis. In vitro, macrophage movement is arrested by one class of lymphokines known as macrophage migration inhibitory factors (MIFs). We report here the purification of milligram quantities of a unique multifunctional protein from rat liver which links enzymatic and immunological detoxification systems. This protein actuates both GST and MIF activity and matches the primary structure of a human MIF in 25 out of 26 amino-terminal amino acids. Primary structure comparisons revealed significant similarity between GSTs and MIF. The glutathione affinity chromatography purification described here yields a 100-fold increase in obtaining MIF and will aid understanding of its precise biological function.     

AgNO3和低温处理对小麦细胞GST及GR酶活性的影响

研究了AgNO3和低温处理对小麦悬浮细胞谷胱甘肽转移酶(GST)及谷胱甘肽还原酶(GR)酶活性的影响.结果表明,AgNO3和低温处理对小麦细胞再生的影响因处理时间的不同而有差异,在处理的4 d内低温处理使再生率明显增加,AgNO3处理2 d使细胞再生率显著增高,但处理4 d则对细胞再生无明显影响.低温处理使细胞蛋白质含量明显升高,AgNO3处理对小麦细胞蛋白质含量无明显影响.小麦细胞GST活性随处理时间的延长而迅速降低,AgNO3处理对GST活性无明显影响,但低温处理明显延缓GST活性降低.AgNO3和低温处理都使小麦细胞GR酶活性明显降低.AgNO3处理2 d和低温处理对细胞谷胱甘肽(GSH)含量无明显影响,但在处理的第4 d AgNO3使细胞GSH含量明显降低.     

Tertiary structural similarity between a class A beta-lactamase and a penicillin-sensitive D-alanyl carboxypeptidase-transpeptidase

beta-Lactam antibiotics--the penicillins, cephalosporins and related compounds--act by inhibiting enzymes that catalyse the final stages of the synthesis of bacterial cell walls. Recent crystallographic studies of representative enzymes are beginning to reveal the structural bases of antibiotic specificity and mechanism of action, while intensive efforts are being made to understand the beta-lactamase enzymes that are largely responsible for bacterial resistance to these antibiotics. It has been suggested that the beta-lactamases and beta-lactam target enzymes may be evolutionarily related and some similarity of amino-acid sequence around a common active-site serine residue supports this idea. We present here the first evidence from a comparison of three-dimensional structures in support of this hypothesis: the structure of beta-lactamase I from Bacillus cereus is similar to that of the penicillin-sensitive D-alanyl-D-alanine carboxypeptidase-transpeptidase from Streptomyces R61.     

Mandelate racemase and muconate lactonizing enzyme are mechanistically distinct and structurally homologous

Mandelate racemase (MR) and muconate lactonizing enzyme (MLE) catalyse separate and mechanistically distinct reactions necessary for the catabolism of aromatic acids by Pseudomonas putida. The X-ray crystal structure of MR, solved at 2.5 A resolution, reveals that the secondary, tertiary and quaternary structures of MR and MLE are remarkably similar; also, MR and MLE are about 26% identical in primary structure. However, MR has no detectable MLE activity and vice versa. Thus, MR and MLE constitute the first example of enzymes that catalyse different reactions, as opposed to mechanistically identical reactions on different substrates, yet possess sufficient structural and sequence identity that they are likely to have evolved from a common ancestor. The discovery that MR and MLE catalyse different reactions but share a common structural framework has broad implications for the natural evolution of enzymes and metabolic pathways, as well as for the rational modification of enzyme activities.