【作者】 冯德日；

【导师】 刘兰英；

【作者基本信息】 吉林大学 ， 生物化学与分子生物学， 2006， 硕士

【摘要】 谷胱甘肽过氧化物酶(GPX)是机体内重要的抗氧化酶之一,对防治由活性氧引起的各种疾病具有潜在的应用价值。目前国际上已研制了多种GPX模拟物如PZ51,Desferal-Mn,硒化环糊精等。这些模拟物虽具有稳定性好、分子量小等优点,但其GPX活性普遍较低,且对机体有一定的毒副作用。我们以透明质酸(Hyaluronic acid, HA)为酶模型首次合成了一种新的GPX模拟物—硒化透明质酸(SeHA),其GPX活力可达276 U/umol,是目前已报道的所有合成模拟酶中GPX活力最高的的化合物。且与其它的GPX酶模拟物相比,由于透明质酸是生物体内存在的物质,SeHA还具有毒性小、水溶性及组织相容性好等其它一些优点。本文建立了两种不同的体外生物损伤体系:Fe2+/Vc诱导的线粒体损伤体系及H2O2诱导的红细胞氧化溶血体系,用以研究SeHA的生物活性。结果显示在两种不同的体外损伤体系中SeHA都表现出了显著的生物活性,且在与谷胱甘肽(GSH)、维生素C(Vc)等抗氧化剂以及GPX模拟物-PZ51的比较中,SeHA表现出的抗氧化活性是最显著的,这充分显示了SeHA作为一种我们首次合成的GPX模拟酶,在治疗由活性氧引起的各种相关性疾病方面将具有重要的应用前景,为开发出新型的高效抗氧化药物奠定基础。更多还原

【Abstract】 Reactive oxygen species (ROS) are products of the normal metabolicactivities of aerobicliving organism and are produced in response to variousstimuli.Under normal conditions, there is a balance between the production ofROS and their destruction.In certain pathogenic states the production of ROS isenhanced and the excess ROS damage biomacromolecules such as RNA, DNA,protein, sugars and lipids, and this results in ROS-mediated diseases.ROSrelated-diseases include reperfusion injury, inflammatory process, age-relateddiseases, neuronalapoptosis, cancer and cataract. In order to scavenge the ROS,the living organism has sever allines of defense system, including enzymatic andnon-enzymatic action.GPX react very important role in the metabolic activitiesof ROS, it can eliminate H2O2 and ROOH.A lot of evidence demonstrate thatthe ability of GPX to eliminate H2O2 is much stronger than CAT and others.Dueto the limitations associated with native GPX (solution instability, limitedcellular accessibility, immunogenicity, short half-lives, costs of production, andproteolyticdigestion).Scientists have made a great deal of efforts to study thestructure-activity correlation of native GPX, prepared many GPX mimics andstudied the biological effects of GPX mimics.At present, some GPX mimics have been devised, such as Ebselen 、Desferal-Mn and 2-selenium of cyclodextrin .Ebselen is a well-known GPXmimic, but its GPX activity is only about 1 U/μmol.Due to only considerationof chemic al property not consideration of catalytic mechanism and function ofenzyme, most mimics have very low GPX activity.Basing on the framework of hyaluronic acid(HA) and method of chemicalmodification, a novel selenide hyaluronic acid (SeHA) was synthesized to befunctioned as a mimic of glutathione peroxidase (GPX) .The structure of SeHAwas characterized by means of IR and NMR with the conclusion that the targetSeH was located at –CH2OH of the N-acetyl-D-glucosamine.The GPXactivities of SeHA was determined to be 276 U/μmol, which is 278 times higherthan that of Ebselen, respectively.SeHA exhibits the highest GPX activityamong the reported small GPX mimics.Because of some advantages of SeHA(high GPX activity, good water solubility, low cost of production, sugarbackbone and so on) , it has great potential in antioxidant drug.Antioxidant activity was studied by using two different model system:ferrous sulfate/ ascorbate-induced mitochondria damage model system and H2O2induced erythrocytes hemolysis and Hydroper-Oxidation model system.Theresult demonstrated that SeHA not only could inhibited the swelling ofmitochondria、reduced the accumulation of MDA、preserved the activity ofcytochrome-coxidase in the mitochondria damage model system, and comparedwith Ebselen, SeHA exhibited more stronger ability to protect the damagedmitochondria.In the H2O2 induced erythrocytes hemolysis and Hydroper-Oxidation model system, SeHA had obvious protection to restrain thehemolysis of erythrocytes、avoid the decrease of hemoglobin、inhibite the lipidperoxidation of damage erythrocytes.The ability of SeHA to protect vivalagainst oxidative damage is obviously stronger than other antioxidants, such asEbselen、GSH.These result demonstrate that, as a kind of new GPX mimic,SeHA will react very important role in the ROS-mediated diseases therapy.更多还原