壳寡糖可降低阿尔茨海默症模型细胞内活性氧水平

用荧光显微成像测量了两种阿尔茨海默症（Alzheimer's disease,AD）模型细胞即swe型N2a细胞和Δ9/swe型N2a细胞中活性氧的水平。培养液中适当浓度的壳寡糖降低了两种模型细胞中的活性氧水平,这一抑制作用随壳寡糖浓度的变化而变化。壳寡糖对两种模型细胞作用存在差别,提示壳寡糖抑制AD模型细胞内活性氧可能有不同的途径。     

Effect of Rhinovirus Challenge on Antioxidant Enzymes in Respiratory Epithelial Cells

The host inflammatory response appears to be an important contributor to the pathogenesis of human viral respiratory illness. Virus-induced oxidative stress appears to mediate an early phase of elaboration of the proinflammatory cytokine interleukin-8 by respiratory epithelial cells. The purpose of these studies was to determine if virus-induced alterations in either the expression or function of antioxidant enzymes contributes to the cellular oxidative stress following rhinovirus challenge. The activities of Mn superoxide dismutase (MnSOD), catalase and glutathione peroxidase (GPX) were not significantly changed by rhinovirus challenge. CuZn superoxide dismutase (CuZnSOD) activity six hours after challenge was 2.55 &#45 0.56 U/mg protein in rhinovirus-challenged cells compared to 1.16 &#45 0.54 U/mg protein in control cells ( p =0.029). This increased activity was associated with a concomitant increase in CuZnSOD mRNA and protein concentration. These data suggest that rhinovirus-induced changes in the host cell redox state that result in the early elaboration of interleukin-8 are not mediated by inhibition of either the expression or function of these antioxidant enzymes.     

Effect of Polyphenols on the Growth and Enzymes of Some Animal Cells

The effect was investigated of some polyphenol compounds on the growth and intracellular enzyme activity of human-derived cells and Chinese hamster ovary (CHO) cells. Quercetin, a mutagen, inhibited the growth of serum-free cultured human-human hybridomas (SI102 and HB4C5) and a human histiocytic lymphoma cell line (U-937), but did not affect the growth of CHO cells. Glycosides of quercetin such as quercetin-4′-glucoside (Q-4′-G), quercetin-3,4′-glucoside (Q-3,4′-G) and rutin, and other polyphenol compounds (catechin and epicatechin) had no significant inhibiting effect on the growth of human-derived cells or CHO cells. These compounds slightly promoted the growth of human-derived cells. Most of the polyphenols used increased the activity of a drug-metabolizing enzyme, NADPH-cytochrome C reductase, in the U-937 cells and CHO cells, this effect being more marked in the CHO cells than in the U-937 cells. Quercetin markedly reduced the activity of catalase in the human-derived cell lines, while it slightly activated catalase in the CHO cells. Rutin, Q-4′-G, Q-3,4′-G, catechin and epicatechin produced no significant change in catalase activity. Quercetin also reduced the activity of glutamic oxaloacetic transaminase in the U-937 cells.     

Effect of the Rhizobium leguminosarum252 Agglutinins on the Activity of Certain Enzymes in Plant Cells

The incubation of pea seedling roots with the surface agglutinins R₁and R₂of Rhizobium leguminosarum252 brought about an increase in the activity of proteases, -glucosidase, and, especially, succinate dehydrogenase in the roots. The data presented show that rhizobial agglutinins play an important part in the formation and functioning of legume–rhizobial associations.     

The sixth HAMP domain negatively regulates the activity of the group III HHK containing seven HAMP domains

In fungi, the group III hybrid histidine kinases (HHK) act as important sensors to regulate osmoadaptation, hyphal growth, morphogenesis, conidia formation and virulence. They are molecular targets for antifungal agent fludioxonil. They typically have HAMP domain repeats at the NH₂-terminus that are important for their activity. Interestingly, the numbers of HAMP domain vary among the orthologs from different genera. The orthologs from basidiomycetes harbor seven HAMP domains whereas those from yeast contain five HAMP domains. In order to understand the functioning of a seven-HAMP module, we have constructed a yeast-like chimera DhNik1–Tco1 containing seven HAMP domains. The functional characterization of this chimera in yeast Saccharomyces cerevisiae showed that the sixth HAMP domain played important regulatory role. Our results indicated that the negative regulation of histidine kinase activity by the penultimate HAMP domain could possibly be an evolutionarily conserved theme in the group III HHK containing different lengths of poly HAMP module.     

The Effect of Copper on the mRNA Expression Profile of Xenobiotic-Metabolizing Enzymes in Cultured Rat H4-II-E Cells

Copper (Cu²⁺) is an essential element that plays important roles in physiological functions of the body. However, high Cu²⁺ levels can have toxic implications. This study aims to investigate the constitutive response to Cu²⁺ exposure of xenobiotic-metabolizing enzymes in cultured rat liver (H4-II-E) cell lines. Rat cells were exposed to copper sulfate (0–500 μM) for 24 h. The effects of Cu²⁺ on the messenger RNA (mRNA) expressions of phase I and II enzymes and regulatory elements were examined using real-time PCR. Metallothionein mRNA expression was induced in a dose-dependent manner after treatment with Cu²⁺. mRNA expressions of phase I enzymes such as cytochrome P450 1A1 and 1A2 (CYP1A1 and CYP1A2) were slightly induced after exposure to low concentrations of Cu²⁺; however, CYP1A1 and CYP1A2 mRNA expressions were significantly downregulated at higher Cu²⁺ concentrations. These effects corresponded with expression of aryl hydrocarbon receptor mRNA. The mRNA expressions of phase II enzymes were reduced upon exposure to Cu²⁺. In conclusion, phase I and II enzyme expressions were significantly modulated upon Cu²⁺ exposure. These results indicated that Cu²⁺ exposure had toxicological implications for cultured H4-II-E cells.     

补肾活血法对AD模型小鼠行为学的影响

目的:研究中医补肾活血法指导下中药复方(益智健脑方浓缩液)以及针刺("补肾活血针刺法")对阿尔茨海默病模型小鼠SAMP8(Senescgnce Accelerated Mouse P8,SAMP8)的行为学影响,从不同侧面阐明补肾活血法对SAMP8小鼠的治疗作用以及防治AD的可行性.方法:将5月龄雄性SAMP8 30只随机分为中药治疗组(n=10)、针刺治疗组(n=10)和模型对照组(n=10),中药治疗组以益智健脑方浓缩液灌胃;针刺治疗组予以"补肾活血针刺法"干预;模型对照组不予任何处理;另设5月龄雄性SAMR1小鼠(n=10)作为正常对照组.4周后,采用Morris水迷宫对各组小鼠的行为学进行检测分析其学习记忆能力的变化.结果:Morris水迷宫实验中,模型对照组SAMP8小鼠的逃避潜伏期较正常对照组SAMR1小鼠的逃避潜伏期时间明显延长(P<0.05),停留在原平台象限的时间和穿越原平台次数较正常对照组SAMR1小鼠明显减少(P<0.05);补肾活血法指导下,采用中药复方益智健脑方浓缩液以及"补肾活血针刺法"干预均能够明显缩短SAMP8小鼠的逃避潜伏期(P<0.05),增加其停留在原平台象限的时间和穿越原平台次数(P<0.05).结论:补肾活血法能够明显改善AD模型小鼠SAMP8的学习记忆能力以及记忆巩固、再现能力.     

植物淀粉合成的调控酶

淀粉是植物中最普通的碳水化合物,是人类最主要的食品来源与重要的工业原料。植物淀粉的生物合成主要涉及了4种酶—ADPG焦磷酸化酶、淀粉合成酶、淀粉分支酶和淀粉去分支酶,它们在淀粉的生物合成中发挥着不同作用。近年来,随着基因工程技术的迅速发展及与这些酶有关的众多突变体的发现,使人们对这些酶的结构、特性、功能及表达调控等方面的研究取得了重要进展。并且,人们已开始利用基因工程技术调控植物淀粉的数量与特性,取得了一定成效。在此,文章介绍了调控植物淀粉合成关键酶的生化特性、基因调控及利用基因工程改良植物淀粉等方面所取得进展。     

High Glucose Triggers Nucleotide Imbalance through O-GlcNAcylation of Key Enzymes and Induces KRAS Mutation in Pancreatic Cells

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Proteolytic Enzymes in Growing Root Cells

The experimental material consisted of fifteen serial sections,each 1·o mm. in length, cut from the apex towards thebase of the bean root. Proteolytic enzymes were assayed at variouspH levels on corresponding groups of sections. Values per sectionwere converted to average values per cell by dividing each bythe number of cells occurring in the section. Evidence was obtainedfor the presence of two proteolytic enzymes or groups of enzymeswith different pH optima. Maximum activity of proteolytic enzymesis shown by cells which have ceased to grow and in which thelevel of protein and certain other enzymes is falling. The significanceof these observations in the interpretation of a mechanism ofcell growth is discussed.     

A mutational wrench in the HAMP gearbox

HAMP domains communicate between input and output signalling elements in bacterial proteins. In the Tsr chemoreceptor, they convert axial movement of transmembrane helix 2 into changes in packing of the cytoplasmic kinase-control module (KCM). Zhou et al . suggest transmembrane helix 2 'tugs' on HAMP to destabilize x-da packing of the parallel four-helix bundle of the HAMP homodimer. Attractants would inhibit tugging. HAMP stability may be inversely related to stability of the a-d packing of the anti-parallel four-helix bundle of KCM, a relationship possibly facilitated by HAMP/KCM helical mismatch. The beauty of this idea lies in its simplicity and testability.     

Nucleolytic Enzymes in Growing Root Cells

Experimental material consisted of fifteen serial sections 1.0mm. in length, cut from the apex towards the base of bean rootsof standard length. Optimum pH for ribo- and deoxyribonucleaseswere determined. Each enzyme was assayed at optimum pH in correspondinggroups of sections, and the enzyme activity per cell calculated.Results are compared with those obtained using other tissuesand with those of earlier investigations of the enzyme complementof the bean root.     

1,3-丙二醇生物法生产中关键酶的研究进展

目前,国内外对于1,3-丙二醇(1,3-propanediol,1,3-PD)的生产研究正在由化学法逐渐向生物法转变。该文着重介绍了生物法生产1,3-PD的生产菌株和生物合成途径,综述了关键酶的性质特点和基因克隆表达情况,对关键酶晶体结构的相关研究成果进行了介绍,进一步探讨了运用宏基因组技术和酶分子改造技术来获得新型高性能关键酶的方法,并展望了基因工程菌的应用前景,从而推动了对1,3-PD生产途径中关键酶的了解及1,3-PD的生产应用研究。     

Inhibition of Trypsin-Like Enzymes on Cells with Rhodamine-Aprotinin

Abstract

Aprotinin, a polypeptide inhibitor of trypsin-like enzymes, has been labelled with rhodamine. Rhodamine-aprotinin inhibits trypsin in free solution in an identical manner to aprotinin. Rhodamine-aprotinin binds to trypsin-like enzymes on cells in formaldehyde fixed wax embedded sections. This technique has been used to locate cells possessing trypsin-like enzymes by means of fluorescent microscopy. In the present study we have used this technique to locate tumour cells.     

萜烯生物合成中关键酶的研究进展*

萜烯类化合物是一类高度多样化的天然产物,具有抗肿瘤、抗氧化及免疫调节等生理活性,因此被广泛应用于医药健康、食品、化妆品领域。然而,直接从自然资源中获取萜烯类化合物效率低、成本高,且往往对生态环境产生不利影响,不能实现绿色可持续生产。微生物合成萜烯类化合物近年来备受关注,研究人员从合成途径的构建与调控、关键酶的理性及半理性改造、发酵工艺优化等多个方面进行了探究,取得了丰硕的成果。其中,合成途径中关键酶的催化效率是影响微生物生产萜烯类化合物的重要因素。针对关键酶的研究对于提高微生物合成萜烯类化合物的能力,推动该类天然产物微生物生产的大规模应用具有重要意义。对萜烯类化合物合成途径中的3-羟基-3-甲基戊二酰辅酶A还原酶(HMGR)、1-脱氧-D-木酮糖-5-磷酸合酶(DXS)、异戊二烯基二磷酸合成酶(IDS)和萜烯合酶(TPS)4种关键酶的研究进行了综述,并总结讨论了如何通过代谢工程和蛋白质工程手段以及合成生物学技术调节关键酶的催化活性,提高微生物合成萜烯类化合物的效率,对未来利用微生物合成萜烯类化合物的发展进行了展望。     

植物三萜皂苷生物合成中关键后修饰酶研究进展

三萜皂苷是由三萜苷元、糖基、糖醛酸等组成的C30萜类化合物,是许多药用植物的主要活性成分,具有广泛的药理作用。三萜皂苷的生物合成包括前体和三萜皂苷骨架的形成以及调控皂苷结构多样性的后修饰。三萜皂苷的后修饰包括三萜骨架的氧化/羟基化和糖基化,分别由不同超基因家族编码的细胞色素P450单加氧酶和糖基转移酶进行催化。三萜皂苷通过后修饰最终可形成多种单体皂苷。目前,已在少数植物中识别和确认了个别与三萜皂苷生物合成相关的关键后修饰酶,发现了部分很可能参与后修饰过程的候选基因。该文就近年来国内外有关三萜皂苷生物合成途径关键后修饰酶的研究进行综述,为进一步开展相关研究和对合成精细途径的解析提供参考。