氧化型谷胱甘肽对大鼠硫酸基转移酶1A1与羟基多氯联苯作用的影响  

Influence of oxidized glutathione on rat sulfotransferase 1A1 for interactions with hydroxylated polychlorinated biphenyls

作　　者：刘云岗[1] 姜浩[1] 

机构地区：[1]南方医科大学公共卫生与热带医学学院毒理学系,广州510515

出　　处：《重庆医科大学学报》2011年第10期1161-1165,共5页Journal of Chongqing Medical University

基　　金：广东省高等学校人才引进专项基金资助项目(编号:粤财教[2010]343号)

摘　　要：目的:探讨大鼠硫酸基转移酶(Sulfotransferase,SULT)1A1在巯基部分氧化的状态下对某些羟基多氯联苯(Hydroxy-lated polychlorinated biphenyls,OH-PCBs)的特异性及酶促动力学的影响。方法:大鼠肝胞液作为大鼠SULT的天然来源,大鼠SULT1A1则从重组表达的大肠杆菌分离纯化;硫酸基结合速率以辅酶转化产物3’,5’-二磷酸腺苷的形成来测定;酶蛋白巯基氧化还原状态以氧化型/还原型谷胱甘肽(Oxidized/reduced glutathione,GSSG/GSH)对酶预处理来获得。结果:6’-OH PCB 35、4’-OH PCB 9及4’-OH PCB 12均可在大鼠肝胞液作用下形成硫酸基结合产物;4’-OH PCB 9和2-萘酚在用GSSG预处理的大鼠SULT1A1作用下的硫酸基结合速率降低而底物抑制消除;4’-OH PCB 6在该酶经GSSG预处理后由抑制剂转变为底物,且反应速率随预处理时GSH/GSSG中GSSG的比例增高而增高;4-OH PCB 14则仅在该酶经GSSG预处理后由抑制剂变为底物。结论:大鼠SULT1A1在巯基氧化后可降低OH-PCBs等底物的最大反应速度(Maximal velocity,Vmax),同时消除底物抑制;酶的巯基氧化状态使某些作为抑制剂的OH-PCBs转变为底物,其反应速率与GSSG/GSH相对量有关。Objective：The formation of disulfide bond within protein molecules is an outcome of oxidative stress.This study is to investigate the effects of partial oxidation of the sulfhydryl groups in the rat sulfotransferase（SULT） 1A1 protein on its specificity and enzymatic kinetics toward hydroxylated polychlorinated biphenyls（OH-PCBs）.Methods：Rat liver cytosol was used as the native SULTs,and rat SULT1A1 was extracted and purified from recombinant E.coli cells expressing this enzyme;the enzyme activity was assayed by the formation of 3＇,5＇-diphosphoadenosine,the reaction product of the co-factor of SULTs;the redox status of the sulfhydryl groups in the enzyme protein was modeled by pretreatment of the enzyme with oxidized/reduced glutathione（GSSG/GSH）.Results：6＇-OH PCB 35,4＇-OH PCB 9 and 4＇-OH PCB 12 could be conjugated with sulfate group in the presence of rat liver cytosol;the sulfation of 4＇-OH PCB 9 and 2-naphthol by GSSG-pretreated rat SULT1A1 demonstrated decreased reaction rates and blockage of substrate inhibition.4＇-OH PCB 6 was converted from an inhibitor to a substrate after pretreatment of rat SULT1A1 with GSSG,and the reaction rate increased along with the increase in the ratio of GSSG/GSH present in the pretreatment;for 4-OH PCB 14,pretreatment of the enzyme with pure GSSG was essential for the conversion of an inhibitor to a substrate.Conclusion：After oxidation of the intramolecular sulfhydryl groups,rat SULT1A1-catalyzed sulfation can apparently reduce the maximal velocity（Vmax） of its substrates,such as OH-PCBs,and eliminate substrate inhibition.The oxidation of the enzyme can result in the conversion of some inhibitory OH-PCBs to substrates,and the reaction rate is relevant to the ratio of GSSG/GSH employed for modulating the enzyme.

关 键 词：大肠杆菌 重组硫酸基转移酶 羟基多氯联苯 氧化型谷胱甘肽 

分 类 号：R963[医药卫生—微生物与生化药学]