植物戊糖磷酸途径及其两个关键酶的研究进展

戊糖磷酸途径是植物体中糖代谢的重要途径,主要生理功能是产生供还原性生物合成需要的NADPH,可供核酸代谢的磷酸戊糖以及一些中间产物可参与氨基酸合成和脂肪酸合成等。葡萄糖-6-磷酸脱氢酶和6-磷酸葡萄糖酸脱氢酶是戊糖磷酸途径的两个关键酶,广泛的分布于高等植物的胞质和质体中。本文综述了植物戊糖磷酸途径及其两个关键酶的分子生物学的研究进展,讨论了该途径在植物生长发育和环境胁迫应答中的作用。     

金针菇戊糖磷酸途径的关键基因表达分析

生物细胞主要依靠戊糖磷酸途径(pentose phosphate pathway, PPP)产生还原力,该途径也是细胞内各种单糖分子相互转变和不同结构糖分子合成的重要方式。PPP途径能够在生物的不同生长发育或代谢活动中发挥重要的作用。本研究基于金针菇单核体菌株W23基因组数据,使用KEGG数据库注释了与金针菇PPP途径相关的22个基因。进一步结合生物信息学分析手段,研究了两个限速酶:葡萄糖-6-磷酸脱氢酶(Glucose-6-phosphate 1-dehydrogenase, G6PDH)与6-磷酸葡糖酸脱氢酶(6-phosphogluconate dehydrogenase,6PGDH)基因结构,并利用金针菇不同发育时期的不同组织转录组数据,分析了这两个限速酶编码基因的表达模式。结果表明,两个基因编码蛋白均具有行使其功能的保守结构域,定位在细胞质中,包含多个磷酸化位点。G6PDH系统发育分析表明该基因较为保守,进化与物种分类地位相一致。基因g6pdh与6pgdh的表达量呈高度正相关(相关系数为0.99),两个基因在菌丝阶段的表达量均高于子实体阶段,并且在菌盖中表达量高于菌柄,显示了PPP途径在金针菇不同发育阶段的活跃程度。本研究能够为金针菇生长和发育过程研究提供理论参考。     

磷酸戊糖途径的调节对红豆杉细胞生长及紫杉醇合成的影响

在正常的红豆杉细胞悬浮培养过程,葡萄糖-6-磷酸脱氢酶(G6PDH)活性的变化趋势与生物量的基本相似。而在chitosan处理的细胞中G6PDH活性升高而生物量下降。100 mg·L^-1 chitosan和500mg·L^-1 chitosan均对细胞G6PDH具有诱导作用,且后者的诱导强度较前者的高。乙二醇双2-氨基乙基醚四乙酸(EGTA)的加入降低chitosan对细胞G6PDH的诱导程度,显示chitosan对G6PDH的诱导需要Ca²⁺的参与。谷胱甘肽(GHS)的处理可反馈抑制chitosan对细胞G6PDH的诱导。通过分析调节后G6PDH的各种活性与细胞中紫杉醇产量的关系,认为采用合适的处理方法调节磷酸戊糖途径,有利于红豆杉细胞合成紫杉醇。     

高等植物葡萄糖-6- 磷酸脱氢酶与6- 磷酸葡萄糖酸脱氢酶基因的不同进化起源

葡萄糖-6-磷酸脱氢酶与6-磷酸葡萄糖酸脱氢酶是植物戊糖磷酸途径中的两个关键酶。在克隆了水稻质体葡萄糖-6-磷酸脱氢酶基因OsG6PDH2和质体6-磷酸葡萄糖脱氢酶基因Os6PGDH2基础上,分析比较了水稻胞质和质体葡萄糖-6-磷酸脱氢酶基因和6-磷酸葡萄糖酸脱氢酶基因的基因结构、表达特性和进化地位。结合双子叶模式植物拟南芥两种酶基因的分析结果,认为高等植物葡萄糖-6-磷酸脱氢酶基因和6-磷酸葡萄糖酸脱氢酶基因在进化方式上截然不同,葡萄糖-6-磷酸脱氢酶的胞质基因与动物和真菌等真核生物具有共同的祖先;6-磷酸葡萄糖酸脱氢酶的胞质酶和质体酶基因都起源于原核生物的内共生。讨论了植物葡萄糖-6-磷酸脱氢酶与6-磷酸葡萄糖酸脱氢酶基因可能的进化模式,为高等植物及质体的进化起源提供了新的资料。     

高等植物葡萄糖-6-磷酸脱氢酶与6-磷酸葡萄糖酸脱氢酶基因的不同进化起源

葡萄糖-6-磷酸脱氢酶与6-磷酸葡萄糖酸脱氢酶是植物戊糖磷酸途径中的两个酶.在克隆了水稻质体葡萄糖-6-磷酸脱氢酶基因OsG6PDH2和质体6-磷酸葡萄糖脱氢酶基因Os6PGDH2基础上,分析比较了水稻胞质和质体葡萄糖-6-磷酸脱氢酶基因和6-磷酸葡萄糖酸脱氢酶基因的基因结构、表达特性和进化地位.结合双子叶模式植物拟南芥两种酶基因的分析结果,认为高等植物葡萄糖-6-磷酸脱氢酶基因和6-磷酸葡萄糖酸脱氢酶基因在进化方式上截然不同,葡萄糖-6-磷酸脱氢酶的胞质基因与动物和真菌等真核生物具有共同的祖先;6-磷酸葡萄糖酸脱氢酶的胞质酶和质体酶基因都起源于原核生物的内共生.讨论了植物葡萄糖-6-磷酸脱氢酶与6-磷酸葡萄糖酸脱氢酶基因可能的进化模式,为高等植物及质体的进化起源提供了新的资料.     

蔷薇科植物中山梨醇代谢酶的研究进展

蔷薇科植物中,与山梨醇代谢相关的酶主要有：6-磷酸山梨醇脱氢酶、山梨醇脱氢酶和山梨醇氧化酶。综述了近些年来国内外关于这几种酶的研究进展,涉及的内容有：酶的性质与作用、酶的活性变化与转录的关系,及其在生物技术方面的研究成果,并对今后的研究工作进行了展望。     

二氢硫辛酰转乙酰基酶通过乙酰化磷酸葡糖酸脱氢酶促进核酸合成

丙酮酸脱氢酶复合物(pyruvate dehydrogenase complex,PDC)是位于线粒体内的多酶复合物,催化丙酮酸不可逆地氧化脱羧转为乙酰辅酶A,二氢硫辛酰转乙酰基酶(dihydrolipoyl acetyltransferase,DLAT)是PDC的1个亚基.PDC在细胞线粒体呼吸中发挥关键作用.但是D...     

系列过表达非氧化磷酸戊糖途径基因对重组酿酒酵母菌株木糖代谢的影响

【目的】通过系统研究一个、两个及多个非氧化磷酸戊糖(PP)途径基因组合过表达对酿酒酵母木糖代谢的影响,以优化重组菌株的构建过程,构建高效的木糖代谢酿酒酵母菌株。【方法】在酿酒酵母中双拷贝过表达上游代谢途径的关键酶(木糖还原酶XR,木糖醇脱氢酶XDH,木酮糖激酶XKS),在此基础上构建了一系列PP途径基因过表达菌株,并对其木糖发酵性能进行比较研究。【结果】木糖发酵结果显示,不同组合过表达PP途径基因能不同程度改善重组菌株的木糖发酵性能。其中,过表达PP途径全部基因(RKI1,RPE1,TAL1和TKL1)使菌株的发酵性能最优,其乙醇产率和产量较对照菌株分别提高了39.25%和12.57%,同时较其他基因组合过表达菌株也有不同程度的改善。【结论】通过构建PP途径基因不同组合过表达酿酒酵母菌株,首次对PP途径基因对酿酒酵母木糖代谢的影响进行了系统研究,结果表明,不同组合强化PP途径基因对重组菌株木糖代谢的影响存在差异,相对于其他基因过表达组合,同步过表达PP途径全部基因最有利于碳通量流向乙醇。     

高等植物葡萄糖-6-磷酸脱氢酶的研究进展

葡萄糖-6-磷酸脱氢酶是植物戊糖磷酸途径中的一个关键性调控酶。其主要生理功能是产生供生物合成需要的NADPH及一些中间产物;此外还参与各种生物和非生物胁迫的应答反应。文中主要从葡萄糖-6-磷酸脱氢酶同工酶与调节机制等方面探讨了其生物学功能,再从胁迫耐受、基因克隆、酶的缺失和替代等方面的研究进行综述,并对已发表的高等植物中的G6PDH氨基酸序列进行聚类分析,为今后该酶的研究提供参考。     

杨树葡萄糖-6-磷酸脱氢酶(G6PDH)基因启动子的克隆与分析

葡萄糖-6-磷酸脱氢酶是磷酸戊糖途径的关键性调控限速酶,其主要功能是为脂肪酸合成、氮还原和谷胱甘肽等生物分子合成提供还原力NADPH,也为核酸合成提供戊糖;此外,还参加非生物逆境胁迫应答反应.因此,G6PDH对植物的生长发育起着非常重要的作用.本文利用甜杨G6PDH基因和毛果杨基因组序列,通过PCR获得了甜杨G6PDH基因上游1 400bp的序列.序列分析结果表明,该序列具有启动子的基本元件TATA-bOX、CAAT-box.此外,还包含多个胁迫诱导元件,如低温诱导元件LTR,盐诱导元件GT-1,抗冻、缺水、脱落酸、抗寒元件MYB和MYC,以及光响应元件L-box、G-box、3AF-1、TC丰富区等.     

Coenzyme Specificity of Enzymes in the Oxidative Pentose Phosphate Pathway of Gluconobacter oxydans

The coenzyme specificity of enzymes in the oxidative pentose phosphate pathway of Gluconobacter oxydans was investigated. By investigation of the activities of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) in the soluble fraction of G. oxydans, and cloning and expression of genes in Escherichia coli, it was found that both G6PDH and 6PGDH have NAD/NADP dual coenzyme specificities. It was suggested that the pentose phosphate pathway is responsible for NADH regeneration in G. oxydans.     

Effect of Cadmium on Activities of Some Enzymes of Glycolysis and Pentose Phosphate Pathway in Pea

Activities of alcohol dehydrogenase, hexokinase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase were significantly inhibited by cadmium in germinating pea (Pisum sativum L. cv. Bonneville) seeds. The effect was concentration dependent in the range of 0.25 to 1.0 mM CdCl₂. The magnitude of detrimental effect on these enzymes was reduced during later stage of germination (9 d) largely because of fall in the activities of these enzymes in the control seeds germinated in water. In vitro, activities of hexokinase, glucose-6-phosphate dehydrogenase, and alcohol dehydrogenase were inhibited at 0.5 mM Cd²⁺ in the reaction mixture by 62, 67, and 36 %, respectively, however, 6-phosphogluconate dehydrogenase was insensitive to Cd²⁺. This revised version was published online in June 2006 with corrections to the Cover Date.     

Pentose phosphate metabolism during dormancy breakage in Corylus avellana L.

Commercially obtained fruits of Corylus avellana exhibit the characteristic loss of dormancy of this seed following chilling under moist conditions. The activities of cytosolic and organellar enzymes of pentose phosphate pathway in cotyledonary tissue were assayed throughout stratification and over a similar period in damp vermiculite at 20° C. Glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconic acid dehydrogenase (6PGDH) were both found in cytosolic extracts in all treatments; only 6PGDH was present in the organellar fraction.The enzyme activities monitored in seeds at 20° C remained relatively constant over the course of the investigation except in the case of cytosolic 6PGDH where it is suggested an inhibitor of the enzyme accumulated. This inhibitor was removed by the partial purification procedure. Increases in the activities of the enzymes occurred during stratification, the major increase coinciding exactly with dormancy breakage but prior to the initiation of germination. The marked increase in G6PDH and 6PGDH concurrent with the change in germination potential of the chilled seed may have considerable biochemical significance in breaking down the dormant state.Abbreviations G6P glucose-6-phosphate - G6PDH glucose-6 phosphate dehydrogenase - NADP nicotinamide adenine dinucleotide phosphate - 6 PGDH 6-phosphogluconic acid dehydrogenase - PPP pentose phosphate pathway     

The Functional Significance of the Pentose Phosphate Pathway in Synaptosomes: Protection Against Peroxidative Damage by Catecholamines and Oxidants

Abstract: Catecholamines added in vitro in rat brain synaptosomes activate the decarboxylation of glucose radioactively labelled on carbon 1, suggesting an effective activation of the pentose phosphate pathway. Stimulation also occurred with phenazine methosulphate, reduced glutathione and hydrogen peroxide. The activation of the pentose phosphate pathway by 5-hydroxytryptamine, noradrenaline and dopamine is ascribed to the activation of monoamine oxidase, producing both the respective biogenic aldehyde and hydrogen peroxide. Evidence is presented that the further metabolism of the aldehyde by aldehyde reductase and the removal of hydrogen peroxide by glutathione peroxidase both release the limitation of N ADP⁺ availability for the pentose phosphate pathway by leading to the oxidation of NADPH. The relevance of the maintenance of reduced NADP⁺ on brain is discussed in relation to the metabolism of glutathione and to lipid peroxidation.     

植物类萜生物合成途径及关键酶的研究进展

萜类化合物是植物中广泛存在的一类代谢产物,在植物的生长、发育过程中起着重要的作用。植物中的萜类化合物有两条合成途径:甲羟戊酸途径和5-磷酸脱氧木酮糖/2C-甲基4-磷酸-4D-赤藓糖醇途径。这两条途径中都存在一系列调控萜类化合物生成、结构和功能各异的酶,其中关键酶的作用决定了下游萜类化合物的产量。植物类萜生物合成途径的调控以及该途径中关键酶的研究已成为目前国内外生物学领域的一大热点。综述了植物类萜生物合成途径和参与该途径的关键酶及其基因工程的研究进展,并展望了其应用前景。     

A Metabolic Shift toward Pentose Phosphate Pathway Is Necessary for Amyloid Fibril- and Phorbol 12-Myristate 13-Acetate-induced Neutrophil Extracellular Trap (NET) Formation

Neutrophils are the main defense cells of the innate immune system. Upon stimulation, neutrophils release their chromosomal DNA to trap and kill microorganisms and inhibit their dissemination. These chromatin traps are termed neutrophil extracellular traps (NETs) and are decorated with granular and cytoplasm proteins. NET release can be induced by several microorganism membrane components, phorbol 12-myristate 13-acetate as well as by amyloid fibrils, insoluble proteinaceous molecules associated with more than 40 different pathologies among other stimuli. The intracellular signaling involved in NET formation is complex and remains unclear for most tested stimuli. Herein we demonstrate that a metabolic shift toward the pentose phosphate pathway (PPP) is necessary for NET release because glucose-6-phosphate dehydrogenase (G6PD), an important enzyme from PPP, fuels NADPH oxidase with NADPH to produce superoxide and thus induce NETs. In addition, we observed that mitochondrial reactive oxygen species, which are NADPH-independent, are not effective in producing NETs. These data shed new light on how the PPP and glucose metabolism contributes to NET formation.     

Nicotinamide Adenine Dinucleotide Phosphate Phosphatase Facilitates Dark Reduction of Nitrate: Regulation by Nitrate and Ammonia

Leaves of 15 - 30-d-old plants of sunflower and jute were harvested at 10.00 or 23.00 (local time) and measured immediately, or those harvested at 10.00 were incubated for one hour in sunlight either in water or 5 mM methionine sulfoximine (MSX) solution and then for three hours in dark either in water or 15 mM KNO3 solution. Nitrate feeding during dark incubation, in general, increased nitrate reductase (NR) and nitrite reductase (NiR) activities, and NADH and soluble sugar contents. Increase in tissue nitrate concentration in MSX fed but not in control samples suggested reduction of nitrate in dark. NADPH-dependent NR activity increased considerably upon feeding with nitrate in dark. Concomitantly, NADPH phosphatase activity was also increased in nitrate treated, dark incubated leaves. It is proposed that nitrate regulates dark nitrate reduction by facilitating generation of NADH from NADPH by NADPH phosphatase. High amounts of ammonia accumulated in MSX treated, but not in control leaves, upon dark incubation. Relative activities of NR and NADPH phosphatase, and amounts of soluble sugar and NADH were low in MSX fed samples compared to that of control. So, high amount of ammonia might partially repress NADPH phosphatase and consequently deprive NR of reducing equivalents. This revised version was published online in July 2006 with corrections to the Cover Date.     

Glycerol Phosphate Dehydrogenase, Glucose-6-Phosphate Dehydrogenase, and Lactate Dehydrogenase: Activities in Oligodendrocytes, Neurons, Astrocytes, and Myelin Isolated from Developing Rat Brains

Abstract: Glycerol phosphate dehydrogenase (GPDH), glucose-6-phosphate dehydrogenase (G6PDH), and lactate dehydrogenase (LDH) activities were determined in Oligodendrocytes, neurons, and astrocytes isolated from the brains of developing rats. The activity of each enzyme was significantly lower in both neurons and astrocytes than in Oligodendrocytes. The GPDH activity in Oligodendrocytes increased more than 4-fold during development, and at 120 days cells of this type had 1.4-fold the specific activity of forebrain homogenates. The G6PDH activities in Oligodendrocytes from 10-day-old rats were 1.4-fold the activities in the forebrain homogenates. The activities of this enzyme in Oligodendrocytes were progressively lower at later ages, such that at 120 days the cells had 0.8 times the specific activities of homogenates. The Oligodendrocytes had 0.6 times the homogenate activities of LDH at 10 days, and this ratio had decreased to 0.2 by 120 days. These enzymes were also measured in myelin isolated from 20-, 60-, and 120-day-old rats. By 120 days the specific activities of G6PDH and LDH in myelin were <8% of the respective activities in homogenates. The GPDH activity in myelin was, however, at least 20% the specific activity in the homogenates, even in the oldest animals. It is proposed that LDH could be used as a marker for oligodendroglial cytoplasm in subfractions of myelin and in myelin-related membrane vesicles.