植物iPGAM的研究进展

辅因子非依赖型磷酸甘油酸变位酶(Cofactor-independent phosphoglycerate mutase,iPGAM)是在真菌和高等植物中发现的金属酶,是糖酵解和糖异生过程中的一个关键酶。随着原核生物、无脊椎动物等物种中iPGAM基因被克隆、蛋白晶体结构的解析及其生物学功能的陆续报道,近些年,植物iPGAM的功能开始受到关注。阐述了植物iPGAM蛋白的结构特点及作用机制,着重对已报道的拟南芥、水稻和玉米中iPGAMs的系统进化关系以及生物学功能进行了概述。     

葡萄糖-1-磷酸对灵芝多糖合成的影响

在以葡萄糖为唯一碳源进行灵芝液态发酵时,通过添加不同浓度的代谢中间产物葡萄糖-1-磷酸,研究其对灵芝胞外多糖产量、单糖组成、合成途径相关酶的影响,从而确定影响灵芝多糖单糖组成的关键酶。结果显示,添加葡萄糖-1-磷酸对灵芝多糖产量和多糖的单糖组成并无明显影响。在检测的3种灵芝多糖合成关键酶中,葡萄糖-1-磷酸的添加抑制磷酸葡萄糖变位酶(PGM)、磷酸葡萄糖异构酶(PGI)的酶活,对磷酸甘露糖异构酶(PMI)无明显影响。此外,通过相关性分析后发现,发酵过程中半乳糖和甘露糖比例的变化分别与PGM和PGI、PMI具有相关性。本文结果对实现灵芝多糖代谢的灵活调控提供有益的参考。     

中国人群葡萄糖磷酸变位酶基因频率测定及PGM18-1表型检出

葡萄搪磷酸变位酶(phosphoglucomutase, PGM）是糖元代谢中十分重要的酶,它可逆地 催化下列反应：a-D-葡萄搪-1一磷酸二兰生全 G-1,6-2P a-D-葡萄糖-6-磷酸盐。该酶是由定位于1,4, 6染色单体上PGM PGM PGM,位点上的 等位基因所控制。PGM 广泛分布于体内各种 组织中,其中80-90多为PGM,的基因产物。 红细胞中PGM,编码的同工酶活性与PGM, 活性各占50多,在红细胞中检测不出PG嶙基 因的活性产物。 1964年Spencer等人(47先后证明PGM：具 有多态性。采用淀粉凝胶法检测出PGM, 1, PGM, 2-1和PGM, 2三种遗传表型,它们是 由第1对染色体上PGM,位点上的两个常见 的等位基因PGMi和PGM,所决定。高分辨 的等电聚焦电泳可检出PG城有10种亚型, 是由PGM,位点上的4个等位基因PGMi十、 PGM犷、PG叫十和PG域一所编码121。本文报 告我们应用国产淀粉,采用混合淀粉凝胶方法 测定中国（北京地区）人群的基因频率分布,同 时报道对PGM, 8-1表型的检出。     

不同氮水平下冬小麦叶绿体中甘油醛-3-磷酸脱氢酶活性的变化

NADP-甘油醛-3-磷酸脱氢酶(E.C.1.2.1.13,缩写为G-3-PDH)是卡尔文环中催化光合最初产物3-磷酸甘油酸(3-PGA)还原成3-磷酸甘油醛的关键调节酶,反应如下:     

叶绿体中依赖NAD(P)H的甘油醛-3-磷酸脱氢酶活性的测定

甘油醛-3-磷酸脱氢酶(以下简称GAP脱氢酶)是叶绿体卡尔文环中的一种重要的调节酶,它是卡尔文环中唯一利用由光系统Ⅰ产生的还原能力(NADPH),催化光合作用的最初产物3-磷酸甘油酸(3-PGA)还原成3-磷酸甘油醛,反应如下:     

中国人红细胞磷酸葡萄糖变位酶的电泳分型及其频率研究

磷酸葡萄糖变位酶(Phosphoglucomutase) 是人体组织中广泛存在的一组重要的酶类。它 可以催化葡萄糖一1一磷酸盐和葡萄糖-6-磷酸盐 相互转化,在糖代谢中起着重要的作用11,810 电泳分型表明这种酶存在着多种形式,决 定他们结构的基因座位至少有3个,即PGM PGM PGM,。它们彼此并不连锁,分别定位在 1,4. ,6号染色体上。每一座位分别决定一组特 异的葡萄糖磷酸变位酶的同工酶。酶的总活力 有80-95务是来自PGM,,而其余的主要由 PG喊提供。但在红细胞中PGM;和PGM,大 约各占50外。在所有的组织中PGM,的总活 力比例很少,在红细胞中则检不出来［u.}0 1964年Spencer等人继Hopkinson及Harris 之后证明了红细胞PGM,多态性的存在。他们 利用淀粉凝胶电泳法将其分成3个普通型 PGM, 1-1, PGM, 2-2, PGM, 2-1。这种多态 性是由两种普通的常染色体等位基因（PGM}, PG川）决定的。当PGM;或PG域与不同的 基因座位的一系列罕见等位基因中的某一个等 位基因杂合时,又形成若千稀有型11,5,8]。近年 来,Bark和K{ihnl等人分别采用等电聚焦电 泳技术将PGM,又分成10种遗传表型,并发现 了稀有型及PGM,01710 PGM,的基因频率在不同的群体中各不相 同。应用淀粉凝胶电泳法在英国人群体中检出 58%的PGM, 1一1、36%的PGM,2-1和6 0%o的 PGM, 2-211'。本文报道用醋酸纤维素膜电泳的 方法对中国人群体中红细胞中的PGM：检测结 果,并对血痕进行了分型。PGM,酶型是继 EAP（红细胞酸性磷酸酶）、EsD（醋酶D）之 后用此法检验的第3个酶型。在人类群体遗传 学、法医学的个体识别以及临床医学的基因标 志的研究中有着和上面两种酶同样重要的意 义。     

田菁胶生物合成中的甘露糖磷酸变位酶

用 DE-52和磷酸纤维素亲和层析分离和纯化了甘露糖磷酸变位酶(PMM),非 SDS 凝胶电泳为一条带,但 SDS 凝胶电泳则有三条带,分子量为41500,66000和74000。测定了田菁(Sesbania cannabina)种子的子叶和胚乳中的甘露糖磷酸变位酶和葡萄糖磷酸变位酶(PGM)的活性,并进行了比较,讨论了两种酶的耐温性与田菁胶合成生理活动的相关性。     

生物化学家莱洛伊尔L.F.

著名生化学家莱洛伊尔L.F.(Leloir Luis F.)生于1906年,死于1987年12月4日。他的初期贡献之一且立即引人注目的,是发现了葡萄糖-1,6-二磷酸及葡萄糖-1,6-二磷酸作为磷酸葡萄糖变位酶辅助因子的作用。效仿于此,科里、萨瑟兰和帕斯特纳克一起,提出作为磷酸甘油酸变位酶的2,3双二磷酸甘油酸的类似作用的提议。在莱洛伊尔的重大发     

人磷酸葡萄糖变位酶5对肝癌细胞生长和迁移的影响

目的:构建带有Flag标签的人磷酸葡萄糖变位酶5(PGM5)基因的真核表达载体,研究PGM5对肝癌细胞生长、迁移的影响。方法:以人乳腺文库为模板,采用PCR技术扩增PGM5基因编码序列,酶切后插入pcDNA3.0-Flag载体;将空载体与重组质粒分别转染293T细胞,Western印迹检测PGM5的表达;CCK8生长曲线实验研究PGM5对肝癌细胞生长的影响,细胞划痕实验检测PGM5对肝癌细胞迁移的影响。结果:双酶切及测序结果显示pcDNA3.0-Flag-PGM5真核表达载体构建成功;Western印迹表明PGM5在293T细胞中获得表达;生长曲线和划痕实验显示PGM5可以显著抑制肝癌细胞的生长和迁移。结论:构建了pcDNA3.0-Flag-PGM5表达载体,并发现PGM5可以抑制肝癌细胞生长和迁移,为进一步研究PGM5在癌症发生发展中的作用奠定了基础。     

鄂温克人红细胞ESD和PGM、表型分布及基因频率的研究

人类红细胞醋酶D(ESD）和葡萄糖磷酸变 位酶-1(PGM,）的多态性及其基因足位已被阐 明〔1,4.5,6]。由于它们按孟德尔定律进行遗传,现 已成为群体遗传学、法医学等方面重要的基因 标志。用来进行个体识别,亲权鉴定及探讨族 源、民族融合、迁移都具有重要价值。在我区自 然科学基金资助下,我们对鄂温克族人红细胞 ESI）和PGM,分型进行了调查。     

1H and 51V NMR studies of the interaction of vanadate and 2-vanadio-3-phosphoglycerate with phosphoglycerate mutase.

The formation of complexes of vanadate with 2-phosphoglycerate and 3-phosphoglycerate have been studied using 51V nuclear magnetic resonance spectroscopy. Signals attributed to two 2,3-diphosphoglycerate analogues, 2-vanadio-3-phosphoglycerate and 2-phospho-3-vanadioglycerate, were detected but were not fully resolved from signals of inorganic vanadate and the anhydride formed between vanadate and the phosphate ester moieties of the individual phosphoglycerates. Equilibrium constants for formation of the two 2,3-bisphosphate analogues were estimated as 2.5 M-1 for 2-vanadio-3-phosphoglycerate and 0.2 M-1 for 2-phospho-3-vanadioglycerate. The results of the binding study are fully consistent with non-cooperativity in the binding of vanadiophosphoglycerate to the two active sites of phosphoglycerate mutase (PGM). 2-Vanadio-3-phosphoglycerate was found to bind to the dephospho form of phosphoglycerate mutase with a dissociation constant of about 1 x 10(-11) M at pH 7 and 7 x 10(-11) M at pH 8. Three signals attributed to histidine residues were observed in the 1H NMR spectrum of phosphoglycerate mutase. Two of these signals and also an additional signal, tentatively attributed to a tryptophan, underwent a chemical shift change when the vanadiophosphoglycerate complex was bound to the enzyme. The results obtained here are in accord with these vanadate-phosphoglycerate complexes being much more potent inhibitors of phosphoglycerate mutase than either monomeric or dimeric vanadate. The dissociation constant of 10(-11) M for 2-vanadio-3-phosphoglycerate is about 4 orders of magnitude smaller than the Km for PGM, a result in accordance with the vanadiophosphoglycerates being transition state analogues for the phosphorylation of PGM by 2,3-diphosphoglycerate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Structural studies on a 2,3-diphosphoglycerate independent phosphoglycerate mutase from Bacillus stearothermophilus.

Phosphoglycerate mutase (PGM), an important enzyme in the glycolytic pathway, catalyzes the transfer of a phosphate group between the 2 and the 3 positions of glyceric acid. The gene coding for the 2, 3-diphosphoglycerate independent monomeric PGM from Bacillus stearothermophilus (57 kDa), whose activity is extremely pH sensitive and has an absolute and specific requirement for Mn2+, has been cloned and the enzyme overexpressed and purified to homogeneity. Circular dichroism studies showed at most only small secondary structure changes in the enzyme upon binding to Mn2+ or its 3-phosphoglycerate substrate, but thermal unfolding analyses revealed that Mn2+ but not 3-phosphoglycerate caused a large increase in the enzyme's stability. Diffraction-quality crystals of the enzyme were obtained at neutral pH in the presence of 3-phosphoglyceric acid with ammonium sulfate as the precipitating agent; these crystals diffract X rays to beyond 2.5-A resolution and belong to the orthorhombic space group C2221 with unit cell dimensions, a = 58.42, b = 206.08, c = 124.87 A, and alpha = beta = gamma = 90.0 degrees. The selenomethionyl version of the B. stearothermophilus protein has also been overexpressed, purified, and crystallized. Employing these crystals, the determination of the three-dimensional structure of this PGM by the multiwavelength anomalous dispersion method is in progress.     

Characterization of cofactor-dependent and cofactor-independent phosphoglycerate mutases from Archaea

Phosphoglycerate mutases (PGM) catalyze the reversible conversion of 3-phosphoglycerate and 2-phosphoglycerate as part of glycolysis and gluconeogenesis. Two structural and mechanistically unrelated types of PGMs are known, a cofactor (2,3-bisphosphoglycerate)-dependent (dPGM) and a cofactor-independent enzyme (iPGM). Here, we report the characterization of the first archaeal cofactor-dependent PGM from Thermoplasma acidophilum, which is encoded by ORF TA1347. This ORF was cloned and expressed in Escherichia coli and the recombinant protein was characterized as functional dPGM. The enzyme constitutes a 46 kDa homodimeric protein. Enzyme activity required 2,3-bisphosphoglycerate as cofactor and was inhibited by vanadate, a specific inhibitor of dPGMs in bacteria and eukarya; inhibition could be partially relieved by EDTA. Histidine 23 of the archaeal dPGM of T. acidophilum, which corresponds to active site histidine in dPGMs from bacteria and eukarya, was exchanged for alanine by site directed mutagenesis. The H23A mutant was catalytically inactive supporting the essential role of H23 in catalysis of the archaeal dPGM. Further, an archaeal cofactor-independent PGM encoded by ORF AF1751 from the hyperthermophilic sulfate reducer Archaeoglobus fulgidus was characterized after expression in E. coli. The monomeric 46 kDa protein showed cofactor-independent PGM activity and was stimulated by Mn²⁺ and exhibited high thermostability up to 70°C. A comprehensive phylogenetic analysis of both types of archaeal phosphoglycerate mutases is also presented.     

Molecular dynamics simulation of interactions in glycolytic enzymes

Two glycolytic enzymes, phosphoglycerate mutase (PGM) and enolase from Saccharomyces cerevisiae, have been chosen to detect complex formation and possible channeling, using molecular dynamics simulation. The enzymes were separated by 10 angstroms distance and placed in a water-filled box of size 173 x 173 x 173 angstroms. Three different orientations have been investigated. The two initial 3-phosphoglycerate substrate molecules near the active centers of the initial structure of PGM have been replaced with final product (2-phosphoglycerate) molecules, and 150 mM NaCl together with three Mg2+ ions have been added to the system to observe post-catalytic activity under near-physiological conditions. Analysis of interaction energies and conformation changes for 3 nsec simulation indicates that PGM and enolase do show binding affinity between their near active regions, which is necessary for channeling to occur. Interaction of the C-terminal residues Ala239 and Val240 of PGM (which partially "cap" the 2-phosphoglycerate) with enolase also favors the existence of channeling.     

Investigation of interaction between enolase and phosphoglycerate mutase using molecular dynamics simulation

Two glycolytic enzymes, phosphoglycerate mutase (PGM) and enolase from Saccharomyces cerevisiae have been chosen to detect complex formation between active centers (a/c), using molecular dynamics simulation. Enzymes have been separated by 10 A distance and placed in a water box of size 173 x 173 x 173 A. Three different orientations where a/c of PGM and enolase were positioned toward each other have been used for investigation. The two initial 3-phosphoglycerate substrates at near active centers of initial structure of PGM have been replaced with final 2-phosphoglycerate products. 150mM of NaCl have been added to the system to observe binding activity in the near physiological conditions. Analysis of interaction energies and conformation changes for 3ns simulation indicates that PGM and enolase do show binding affinity between their near active regions. Moreover the similarity between final conformations of the first two orientations with the initial conformation of the third orientation suggests that complex formation between a/c of enzymes is not confined only by discussed orientations. Clear interaction of enolase with C-terminal tail of PGM has been recorded. These results suggest that substrate direct transfer mechanism may exist between enzymes.     

2-Carboxy-D-arabinitol 1-phosphate (CA1P) phosphatase: evidence for a wider role in plant Rubisco regulation

The genes for CA1Pase (2-carboxy-D-arabinitol-1-bisphosphate phosphatase) from French bean, wheat, Arabidopsis and tobacco were identified and cloned. The deduced protein sequence included an N-terminal motif identical with the PGM (phosphoglycerate mutase) active site sequence [LIVM]-x-R-H-G-[EQ]-x-x-[WN]. The corresponding gene from wheat coded for an enzyme with the properties published for CA1Pase. The expressed protein lacked PGM activity but rapidly dephosphorylated 2,3-DPG (2,3-diphosphoglycerate) to 2-phosphoglycerate. DTT (dithiothreitol) activation and GSSG inactivation of this enzyme was pH-sensitive, the greatest difference being apparent at pH 8. The presence of the expressed protein during in vitro measurement of Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) activity prevented a progressive decline in Rubisco turnover. This was due to the removal of an inhibitory bisphosphate that was present in the RuBP (ribulose-1,5-bisphosphate) preparation, and was found to be PDBP (D-glycero-2,3-pentodiulose-1,5-bisphosphate). The substrate specificity of the expressed protein indicates a role for CA1Pase in the removal of 'misfire' products of Rubisco.     

Molecular characterization of phosphoglycerate mutase in archaea

The interconversion of 3-phosphoglycerate and 2-phosphoglycerate during glycolysis and gluconeogenesis is catalyzed by phosphoglycerate mutase (PGM). In bacteria and eukaryotes two structurally distinct enzymes have been found, a cofactor-dependent and a cofactor-independent (iPGM) type. Sequence analysis of archaeal genomes did not find PGMs of either kind, but identified a new family of proteins, distantly related to iPGMs. In this study, these predicted archaeal PGMs from Pyrococcus furiosus and Methanococcus jannaschii have been functionally produced in Escherichia coli, and characterization of the purified proteins has confirmed that they are iPGMs. Analysis of the available microbial genomes indicates that this new type of iPGM is widely distributed among archaea and also encoded in several bacteria. In addition, as has been demonstrated in certain bacteria, some archaea appear to possess an alternative, cofactor-dependent PGM.     

Crystal structure of human B-type phosphoglycerate mutase bound with citrate

The B-type cofactor-dependent phosphoglycerate mutase (dPGM-B) catalyzes the interconversion of 2-phosphoglycerate and 3-phosphoglycerate in glycolysis and gluconeogenesis pathways using 2,3-bisphosphoglycerate as the cofactor. The crystal structures of human dPGM-B bound with citrate were determined in two crystal forms. These structures reveal a dimerization mode conserved in both of dPGM and BPGM (bisphosphoglycerate mutase), based on which a dPGM/BPGM heterodimer structure is proposed. Structural comparison supports that the conformational changes of residues 13-21 and 98-117 determine PGM/BPGM activity differences. The citrate-binding mode suggests a substrate-binding model, consistent with the structure of Escherichia coli dPGM/vanadate complex. A chloride ion was found in the center of the dimer, providing explanation for the contribution of chloride ion to dPGM activities. Based on the structural information, the possible reasons for the deficient human dPGM mutations found in some patients are also discussed.     

Subtyping of human red cell phosphoglucomutase locus 1 (PGM1) polymorphism: a third PGM1(1) allele common among Twa Pygmies from North Rwanda.

Seventy-eight Twa Pygmies from North Rwanda have been subtyped by acid starch gel electrophoresis for the polymorphism at the phosphoglucomutase locus 1 (PGM1). A third common PGM1(1) allele that has been named PGM1(1Twa) was detected in heterozygous association with both PGM1(1S) and PGM1(1F) alleles. The PGM1(1Twa) product is faster than those of the other two PGM1(1) alleles and has the same electrophoretic mobility as the rare PGM1(6) enzyme. The frequency of PGM1(1Twa) was found to be 0.45.     

Evidence for a light dependent increase of phosphoglucomutase activity in isolated, intact spinach chloroplasts

Phosphoglucomutase (PGM) activity was measured in spinach (Spinacia oleracea L.) chloroplasts. Initial enzyme activity in a chloroplast lysate was 5 to 10% of total activity measured with 1 micromolar glucose 1,6-bisphosphate (Glc 1,6-P₂) in the assay. Initial PGM activity increased 2- to 3-fold when chloroplasts were illuminated for 10 minutes prior to enzyme measurement and then decreased slowly in the dark. Measurements of total enzyme activity were unchanged by prior light treatment. Initial PGM activity from light treated chloroplasts was sufficient to account for in vivo rates of starch synthesis. Changes in PGM activity were affected by stromal pH and orthophosphate concentration. Photosynthetic inhibitors, dl-glyceraldehyde, glycolaldehyde, and glyoxylate, decreased and 3-phosphoglyceric acid increased light induced changes of PGM activity. Dark preincubation of chloroplasts with 10 millimolar dithiothreitol had no effect upon initial PGM activity, suggesting that light effects did not involve a sulfhydryl mechanism. Hexose monophosphate levels increased in illuminated chloroplasts. Activation of PGM in a chloroplast lysate by Glc 1,6-P₂ was maximal between pH 7.5 and 8.5. Stromal concentrations of Glc 1,6-P₂ were between 20 and 30 micromolar for both light and dark incubated chloroplasts and these levels should saturate PGM activity. Light dependent alterations of enzyme activity may be due to changes of phosphorylated PGM levels in the stroma or are the result of changes in residual activity by the dephosphorylated form of the enzyme. The above results indicate that PGM activity in spinach chloroplasts may be regulated by light, stromal pH, and Glc 1,6-P₂ concentration.