化学诱变抗体模拟谷胱甘肽过氧化物酶

用诱变剂苯甲基磺酰氟活化兔抗人ＩｇＭ片段上特殊活性部位的丝氨酸残基,经硒化氢处理,则将丝氨酸转变成 硒代半胱氨酸。诱变后的抗体具有谷胱甘肽过氧化物酶活性,其活性为世界最好的ＧＳＨ－Ｐｘ模拟物ＰＺ５１的７０多倍抗体效价为１：８,与没诱变的抗体相似。     

化学突变具有底物结合部位的单克隆抗体制备含硒抗体酶

开发了一种制备抗体酶的新方法。用二硝基氯苯（ＤＮＣＢ）专一地与谷胱甘肽（ＧＳＨ）的巯基反应,合成出半抗原ＧＳＨ－Ｓ－ＤＮＰ。用戊二醛将半抗原偶联到牛血清白蛋白（ＢＳＡ）上,制成全抗原。再用标准的单抗制备法获得具有ＧＳＨ结合部位的单抗（４Ａ４ＩｇＧ）。用苯甲基磺酞氟（ＰＭＳＦ）和Ｈ２Ｓｅ相继处理该单抗,则将单拉结合部位上的丝氨酸（Ｓｅｒ）突变成硒代半胱氨酸（ＳｅＣｙｓ,因而在单抗结合部位上引入了谷胱甘肽过氧化物酶（ＧＰＸ）的催化基团。突变后的单抗具有ＧＰＸ活性,其活力已达到天然ＧＰＸ的数量级水平。动力学行为也与天然ＧＰＸ类似。这种新的含硒抗体酶有优于ＧＰＸ的一些特点。     

纳米硒对肉鸡肝细胞中细胞谷胱甘肽过氧化物酶活性的影响

以亚硒酸钠和蛋氨酸硒为对照,研究了纳米单质硒(纳米硒)对肉鸡肝细胞中细胞谷胱甘肽过氧化物酶(cGPx)活性的影响。每种硒源分别以0.01、0.05、0.10、0.30、0.50、1.0μmol/L6个硒添加浓度培养肉鸡肝细胞,测定培养后0、24、48、72、96h肉鸡肝细胞cGPx活性。结果显示:亚硒酸钠添加浓度(以硒计)在0.01￣0.10μmol/L、蛋氨酸硒和纳米硒添加浓度(以硒计)在0.01￣0.30μmol/L,cGPx活性随着硒添加浓度的增加而增加;亚硒酸钠添加浓度在0.10￣1.0μmol/L、蛋氨酸硒添加浓度在0.30￣1.0μmol/L,cGPx活性随着硒添加浓度的增加而下降,而纳米硒添加浓度在0.30￣1.0μmol/L,cGPx活性始终保持在高峰平台。结果表明,3种硒源的剂量-效应关系曲线中的最适剂量范围宽度依次为:纳米硒>蛋氨酸硒>亚硒酸钠。     

亚硒酸钠对小麦幼苗中谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性以及谷胱甘肽含量的影响

用1.0 mg·L-1的亚硒酸钠根施小麦幼苗,测定亚硒酸钠对谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性以及还原性谷胱甘肽含量的结果表明,外源亚硒酸钠对麦苗地上部的谷胱甘肽过氧化物酶和谷胱甘肽转硫酶活性均有诱导作用,使麦苗体内的谷胱甘肽含量水平增加.     

含硒抗体酶性质的研究

在成功地制备了具有谷胱甘肽过氧化物酶（ＧＰＸ）活性含硒抗体酶（Ｓｅ－ａｂｚｙｍｅ）的基础上,我们筛选了制备Ｓｅ－ａｂｚｙｍｅ的最佳条件,并对其理化性质及酶学性质和稳定性进行了深入的研究。结果表明,Ｓｅ－ａｂｚｙｍｅ的等电点为６．９５和７．０８,一为１５８ｋｄ;适ＰＨ和最适温度范围比天然酶宽广;抗体酶的贮藏稳定性比天然酶高。高Ｘ射线光电子能谱技术测得在Ｓｅ－ａｂｚｙｍｅ中含硒量为５ｍｏｌＳｅ／ｍｏｌ     

植物谷胱甘肽过氧化物酶研究进展

氧化胁迫可诱导植物多种防御酶的产生,其中包括超氧化物歧化酶(SOD,EC1.15.L1)、抗坏血酸过氧化物酶(APX,EC1.11.1.11)、过氧化氢酶(CAT,E.C.1.11.1.6)和谷胱甘肽过氧化物酶(GPXs,EC1.11.1.9).它们在清除活性氧过程中起着不同的作用.GPXs是动物体内清除氧自由基的主要酶类,但它在植物中的功能报道甚少.最近几年研究表明,植物体内也存在类似于哺乳动物的GPXs家族,并对其功能研究已初见端倪.本文综述了有关GPXs的结构以及植物GPXs功能的研究进展.     

化学修饰单克隆抗体模拟谷胱甘肽过氧化物酶

化学修饰具有底物谷胱甘肽（ＧＳＨ）结合部位的单克隆抗体（４Ａ４）,使其结合部位上的丝氨酸（Ｓｅｒ）转变成谷胱甘肽过氧化物酶（ＧＰＸ）的催化基团硒代半胱氨酸（Ｓｅ－Ｃｙｓ）,因而产生高活力的含硒抗体酶（Ｓｅ－ａｂｚｙｍｅ）．突变的４Ａ４（ｍ４Ａ４）的ＧＰＸ活力达到了天然酶活力的１９％,并对ｍ４Ａ４的酶学性质和动力学性质进行了研究;硒代谷胱甘肽（ＧＳｅＨ）连到４Ａ４结合部位,其ＧＰＸ活力由３．８６Ｕ／μｍｏｌ提高到５９８．９Ｕ／μｍｏｌ用黄嘌呤氧化酶／次黄嘌呤为中心的心肌线粒体自由基损伤模型证明Ｓｅ－ａｂｚｙｍｅ（ｍ４Ａ４）可减轻活性氧对线粒体的损伤。     

谷胱甘肽过氧化物酶的硒代半胱氨酸插入元件

真核生物将硒代半胱氨酸插入蛋白质必需硒代半胱氨酸插入元件（ＳＥＣＩＳ）的参与,后者位于硒蛋白ｍＲＮＡ的３′非翻译区．采用ＲＮＡ折叠程序对１５个谷胱甘肽过氧化物酶基因进行计算机处理发现,其可能的ＳＥＣＩＳ中都具有３段保守碱基ＡＵＧＡ－Ａ（Ｇ）ＡＡ－ＧＡ．根据Ａ（Ｇ）ＡＡ位于顶环或者顶环上游５′臂的突环上,可将ＳＥＣＩＳ分为Ⅰ型和Ⅱ型结构     

Selenium modifies glutathione peroxidase activity and glutathione concentration in mice exposed to ozone-provoked oxidative stress

The aim of this study was to show the direct effect of selenium on glutathione peroxidase (GSH-Px) activity and GSH/GSSG concentrations in 3- and 6-month-old mice. An ozone-oxygen mixture was used to provoke an oxygen stress. To measure the Se-effect mice were gavaged with sodium selenite. GSH-Px activity and total glutathione concentrations were determined in serum and in the postnuclear fraction of liver and lungs. Additionally glutathione concentrations were determined in whole blood. Both ozone and selenium, administered separately, reduced GSH-Px activity in lungs of 6-month-old animals, while in young mice an opposite effect of Se was observed. Ozone administered jointly with Se did not influence GSH-Px activity in 6-month-old mice, while in young, 3-month-old mice, a stimulatory effect in lungs was observed. There were no significant changes in GSH-Px activity in the liver of 6-month-old mice, but the stimulatory effect occurred in young mice treated with Se and Se & ozone jointly. In young mice, ozone (also ozone with Se) augmented glutathione concentrations. The response to ozone and selenium strictly depended on age and the antagonism between selenium and ozone was observed only in a few cases.     

A comparative study on effect of dietary selenium and vitamin E on some antioxidant enzyme activities of liver and brain tissues

Since selenium and vitamin E have been increasingly recognized as an essential element in biology and medicine, current research activities in the field of human medicine and nutrition are devoted to the possibilities of using these antioxidants for the prevention or treatment of many diseases. The present study was aimed at investigating and comparing the effects of dietary antioxidants on glutathione reductase and glutathione peroxidase activities as well as free and protein-bound sulfhydryl contents of rat liver and brain tissues. For 12–14 wk, both sex of weanling rats were fed a standardized selenium-deficient and vitamin E-deficient diet, a selenium-excess diet, or a control diet. It is observed that glutathione reductase and glutathione peroxidase activities of both tissues of the rats fed with a selenium-deficient or excess diet were significantly lower than the values of the control group. It is also shown that free and bound sulfhydryl concentrations of these tissues of both experimental groups were significantly lower than the control group. The percentage of glutathione reductase and glutathione peroxidase activities of the deficient group with respect to the control were 50% and 47% in liver and 66% and 61% in the brain, respectively; while these values in excess group were 51% and 69% in liver and 55% and 80% in brain, respectively. Free sulfhydryl contents of the tissues in both experimental groups showed a parallel decrease. Furthermore, the decrease in protein-bound sulfhydryl values of brain tissues were more pronounced than the values found for liver. It seems that not only liver but also the brain is an important target organ to the alteration in antioxidant system through either a deficiency of both selenium and vitamin E or an excess of selenium alone in the diet.     

Effects of aurothioglucose and dietary se on glutathione S-Transferase activities and glutathione concentrations in chick tissues

Experiments were conducted to determine whether the increased glutathione S-transferase (GSH-T) activity associated with selenium (Se) deficiency is necessarily related to losses in the activity of Se-dependent glutathione peroxidase (SeGSHpx) in chicks. Nutritional Se status was altered in two ways: by treatment with an antagonist of Se utilization, aurothioglucose (AuTG), and by feeding diets containing excess Se. Chicks given AuTG (10–30 mg AU/kg, sc) had growth rates and hepatic GSH concentrations that were comparable to those of saline-treated controls; however, their plasma GSH levels exceeded those of either Se-deficient (6-fold) or-adequate (3-fold) saline-treated chicks. Hepatic SeGSHpx activities of AuTG-treated chicks were hals those of controls under conditions of Se-adequacy; however, this effect was not detected when Se was deficient. Hepatic GSH-T_CDNB (assayed with 1-chloro-2,4-dinitrobenzene) activities of AuTG-treated chicks were significantly greater than those of controls when Se was deficient (i.e., when SeGSHpx activity was 12% of the Se-adequate level); however, deprivation of Se did not affect GSH-T_CDNB activity in the absence of AuTG. chicks fed excess Se (6–20 ppm as Na₂SeO₃) in diets containing either low (2 IU/kg) or adequate (100 IU/kg) VE, showed hepatic GSH-T_CDNB activities and GSH concentrations greater than those of Se-adequate (0.2 ppm Se) chicks by 100% and 40%, respectively. That increased hepatic GSH-T_CDNB activity can occur because of either AuTG or excess Se status under conditions wherein SeGSHpx activity is not affected indicates that the transferase response is not directly related to changes in the peroxidase.     

Selenoprotein expression is regulated at multiple levels in prostate cells

Selenium supplementation in a population with low basal blood selenium levels has been reported to decrease the incidence of several cancers including prostate cancer. Based on the clinical findings, it is likely that the antioxidant function of one or more selenoproteins is responsible for the chemopreventive effect, although low molecular weight seleno-compounds have also been posited to selectively induce apoptosis in transformed cells. To address the effects of selenium supplementation on selenoprotein expression in prostate cells, we have undertaken an analysis of antioxidant selenoprotein expression as well as selenium toxicity in non-tumorigenic prostate epithelial cells （RWPE- 1 ） and prostate cancer cells （LNCaP and PC-3）. Our results show that two of the glutathione peroxidase family members （GPX1 and GPX4） are highly induced by supplemental selenium in prostate cancer cells but only slightly induced in RWPE-1 cells. In addition, GPX 1 levels are dramatically lower in PC-3 cells as compared to RWPE- 1 or LNCaP cells. GPX2 protein and mRNA, however, are only detectable in RWPE-1 cells. Of the three selenium compounds tested （sodium selenite, sodium selenate and selenomethionine）, only sodium selenite shows toxicity in a physiological range of selenium concentrations. Notably and in contrast to previous studies, RWPE-1 cells were significantly more sensitive to selenite than either of the prostate cancer cell lines. These results demonstrate that selenoproteins and selenium metabolism are regulated at multiple levels in prostate cells.     

Lymphocyte glutathione peroxidase activity during exacerbations in multiple sclerosis

Glutathione peroxidase, one of the major antioxidants in the human brain, has been found to have decreased activity in patients suffering from multiple sclerosis (MS). This study compares the activity of lymphocyte glutathione peroxidase (L-GSH-px) in MS patients suffering from acute relapses with clinically stable MS patients and with control patients referred with nondemyelinating neurological diseases. All three groups showed an increase of mean enzymatic activity (MEA) during the observation period. The highest MEA in this study was observed in the MS groups. However, there were no significant differences in the L-GSH-px activity in the three groups. These results are not in accordance with previous investigations, and the need for further research in this field is emphasized.