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51.
用水平淀粉凝胶电泳对290尾Moxostoma属3个种的胭脂鱼进行了磷酸葡萄糖异构酶(PGI)的研究,得到10种电泳表现型(Phenotype),由A与B两个位点控制。A位点向阳极迁移,有a、b、c、d及e5个等位基因;B位点向阴极迁移,有f及g两个等位基因。种间差异明显。 不同采集地区(德克萨斯、佛罗里达及路易斯安那)的鱼类,新鲜材料、冰冻材料及雌雄之间电泳结果无差异。 相似文献
52.
Francis C. Knowles 《Physiologia plantarum》1985,64(2):247-252
The presence of ribulose-5-phosphate epimerase (EC 5.1.3.1, epimerase) in samples of ribose-5-phosphate isomerase (EC 5.3.1.6, isomerase) obtained from spinach ( Spinacea aleracea L. cv. Bloomsdale Long Standing) was determined using (i) a sampling procedure which measured the quantity of xylulose-5-phosphate formed in the reaction mixture and (ii) a coupled enzyme assay in which the rate of oxidation of NADH was measured after establishing steady-state concentrations of xylulose-5-phosphate, dihydroxacetonephosphate and glyceraldehyde-3-phosphate by the action of epimerase, transketolase (EC 2.2.1.1), triosephosphate isomerase (EC 5.3.1.1) and glycerol-3-phosphate dehydrogenase (EC 1.1.1.8). In preparations where the ratio of isomerase to epimerase activities was less than 100, both assay procedures yielded valid indications of epimerase activity. The steady-state assay system was found, however, to seriously underestimate epimerase activity in enzyme preparations which were enriched in isomerase. Cross plots of epimerase activity determined by the sampling and steady-state procedures demonstrated that an inhibitor of the coupling enzyme mixture was formed in the presence of high relative concentrations of the isomerase. The inhibited coupling enzyme mixture was fully active with glycer-aldehyde-3-phosphate. Inhibition of the coupling enzyme mixture was attributed to transketolase. Feedback inhibition of transketolase is proposed to be of physiological significance in the photosynthesis cycle, operating to restrict resynthesis of CO2 -acceptor under conditions where high steady-state concentrations of the intermediates of the photosynthesis cycle are maintained. 相似文献
53.
Satoru Kanai Hiroyuki Toh Toshiya Hayano Masakazu Kikuchi 《Journal of molecular evolution》1998,47(2):200-210
Protein disulfide isomerase (PDI) is an enzyme that promotes protein folding by catalyzing disulfide bridge isomerization.
PDI and its relatives form a diverse protein family whose members are characterized by thioredoxin-like (TX) domains in the
primary structures. The family was classified into four classes by the number and the relative positions of the TX domains.
To investigate the evolution of the domain structures, we aligned the amino acid sequences of the TX domains, and the molecular
phylogeny was examined by the NJ and ML methods. We found that all of the current members of the PDI family have evolved from
an ancestral enzyme, which has two TX domains in the primary structure. The diverse domain structures of the members have
been generated through domain duplications and deletions. 相似文献
54.
L-阿拉伯糖异构酶(L-arabinose isomerase,L-AI)是一种可以催化D-半乳糖为D-塔格糖的胞内异构化酶。随着塔格糖在食品工业中越来越广泛的应用,能够将半乳糖转化为塔格糖的食品级微生物以及食品级来源的L-AI受到更大的关注。文中从各种酸奶制品、泡菜及其他一些食品中采集不同的样品,筛选出1株具有L-AI酶活的食品级菌株,经过生理生化鉴定以及16S rDNA序列测定,确定该菌株为戊糖片球菌,命名为Pediococcus pentosaceus PC-5。以该菌基因组为模板,克隆L-AI基因,并在大肠杆菌BL21成功地异源表达。表达产物经粗提取后,在40℃下加入Mn2+,使D-半乳糖转化为D-塔格糖的转化率为33%。 相似文献
55.
Oxidative folding of fully reduced hirudin (R-Hir, six cysteines) undergoes two distinct stages. A first stage of nonspecific disulfide formation promoted by oxidase converts R-Hir to form 3-disulfide scrambled hirudins (X-Hir) as obligatory intermediates. A second stage of disulfide shuffling catalyzed by isomerase converts X-Hir to the native hirudin (N-Hir). The model of hirudin folding is utilized here to develop an assay system for measuring the activity of disulfide oxidase and isomerase, using high-performance liquid chromatography (HPLC) quantification of R-Hir, X-Hir, and N-Hir. The oxidase assay measures the ability of an oxidase to promote R-HirX-Hir conversion. The molar specific activity is expressed as mol ofR-Hir decrease per mol of oxidase per min. The isomerase assay measures the ability of an isomerase to catalyze X-HirN-Hir transformation. The molar specific activity is expressed as mol ofN-Hir increase per mol of isomerase per min. Alternatively, the recovery of N-Hir in the isomerase assay can be determined by its alpha-thrombin inhibitory activity. Using both HPLC and activity-based assay, we have measured the relative oxidase and isomerase activity of reduced and oxidized glutathione, Cys, Cys-Cys, and reduced and oxidized protein disulfide isomerase (PDI). The molar specific activity of reduced PDI was shown to be 0.1+/-0.01 U, which is consistent with documented data obtained by the scrambled RNase-A-based assay. These proposed assay methods provide alternatives to the limited option of methodologies currently available for measuring oxidase and isomerase activities. A major merit of the proposed assay system is the potential to accommodate the analysis of biological samples. 相似文献
56.
通过碳氮源的不同浓度对重组大肠杆菌E.coil BL21(DE3)发酵产蔗糖异构酶(SIase)的影响,并借助于数学分析软件Design Expert,结合Plackett-Burman试验设计和中心复合试验设计分析法,对蔗糖异构酶的产生菌进行了发酵培养基的优化研究。实验表明,最佳培养基组分为甘蔗糖蜜10.65 g/L,玉米浆22.22 g/L,NaCl 7.57 g/L ,MgSO4·7H2O 0.52 g/L, KH2PO4 4.46g/L,优化后的蔗糖异构酶活力达到29.1U/ml,比LB培养基培养重组大肠杆菌(15U/ml),蔗糖异构酶活力提高了94%,与原始菌大黄欧文菌NX-5相比提高了21.4倍(1.3U/ml)。 相似文献
57.
Families of Czech Landrace (94 litters and 636 offspring) were tested for halothane sensitivity, A-O (S), H, PHI and PGD phenotypes. Informative matings for the estimation of recombination rates between marker loci were selected. The following recombination frequencies were established: S-Phi = 4.8 % (2.5 % -10.7 %);S-H = 6.8 % (4.3 %-11.7 %); Phi-H = 2.6 % (0.9 %-5.3 9%); H-Pgd = 4.4 % (1.6 %-8.0 %). CCCC-overs were observed also between S- Hal, Hal-H andHal - Pgd, but were not found between Phi - Hal. On the basis of these results it has been possible to revise the position of the S locus in this linkage group. The most probable gene order would be: S - Phi - Hal (or Hal - Phi) -H- (P02) - Pgd.
A striking difference was found between the number of halothane-sensitive pigs (87) and Haln Hal n genotypes determined by haplotyping (123). Segregation rates in 19 backcross matings and experimental matings of the animals proved that this difference is mostly due to incomplete CCC or low expression of halothane sensitivity. 相似文献
A striking difference was found between the number of halothane-sensitive pigs (87) and Hal
58.
Shan Jiang Wenjing Xu Zhenzhen Chen Changting Cui Xiaofang Fan Jun Cai Yongsheng Gong Bin Geng 《Journal of cellular and molecular medicine》2021,25(7):3437-3448
Hyperhomocysteinaemia (HHcy)-impaired endothelial dysfunction including endoplasmic reticulum (ER) stress plays a crucial role in atherogenesis. Hydrogen sulphide (H2S), a metabolic production of Hcy and gasotransmitter, exhibits preventing cardiovascular damages induced by HHcy by reducing ER stress, but the underlying mechanism is unclear. Here, we made an atherosclerosis with HHcy mice model by ApoE knockout mice and feeding Pagien diet and drinking L-methionine water. H2S donors NaHS and GYY4137 treatment lowered plaque area and ER stress in this model. Protein disulphide isomerase (PDI), a modulation protein folding key enzyme, was up-regulated in plaque and reduced by H2S treatment. In cultured human aortic endothelial cells, Hcy dose and time dependently elevated PDI expression, but inhibited its activity, and which were rescued by H2S. H2S and its endogenous generation key enzyme-cystathionine γ lyase induced a new post-translational modification-sulfhydration of PDI. Sulfhydrated PDI enhanced its activity, and two cysteine-terminal CXXC domain of PDI was identified by site mutation. HHcy lowered PDI sulfhydration association ER stress, and H2S rescued it but this effect was blocked by cysteine site mutation. Conclusively, we demonstrated that H2S sulfhydrated PDI and enhanced its activity, reducing HHcy-induced endothelial ER stress to attenuate atherosclerosis development. 相似文献
59.
Anna Filonova Paul Haemsch Christin Gebauer Wolfram Weisheit Volker Wagner 《植物生理与分子生物学学报》2013,(5):1503-1517
Protein disulfide isomerases (PDIs) are known to play important roles in the folding of nascent proteins and in the formation of disulfide bonds. Recently, we identified a PDI from Chlamydomonas reinhardtii (CrPDI2) by a mass spectrometry approach that is specifically enriched by heparin affinity chromatography in samples taken during the night phase. Here, we show that the recombinant CrPDI2 is a redox-active protein. It is reduced by thioredoxin reductase and catalyzes itself the reduction of insulin chains and the oxidative refolding of scrambled RNase A. By immunoblots, we confirm a high-amplitude change in abundance of the heparin-bound CrPDI2 during subjective night. Interestingly, we find that CrPDI2 is present in protein complexes of different sizes at both day and night. Among three identified interac- tion partners, one (a 2-cys peroxiredoxin) is present only during the night phase. To study a potential function of CrPDI2 within the circadian system, we have overexpressed its gene. Two transgenic lines were used to measure the rhythm of phototaxis~ In the transgenic strains, a change in the acrophase was observed. This indicates that CrPDI2 is involved in the circadian signaling pathway and, together with the night phase-specific interaction of CrPDI2 and a peroxiredoxin, these findings suggest a close coupling of redox processes and the circadian clock in C. reinhardtii. 相似文献
60.