L-谷氨酸对L-苯丙氨酸的热力学及晶型转化的影响

采用静态法测定了L-谷氨酸对L-苯丙氨酸热力学的影响,并应用常用的方程进行了拟合。结果表明,L-谷氨酸的加入增大了L-苯丙氨酸在水中的溶解度。考察了L-谷氨酸对L-苯丙氨酸晶型转化过程的影响,L-谷氨酸的加入可抑制其晶型转化。同时,应用Langmuir模型对晶型转化数据进行了拟合,拟合结果良好,可用于相关数据预测。     

L-谷氨酸-5-甲酯金属化合物的合成、表征和生物活性

在仿自然的条件下,合成了上L-谷氨酸-5-甲酯.对L-谷氨酸-5-甲酯晶体进行了X-射线单晶衍射测定.测量表明,L-谷氨酸-5-甲酯属单斜晶系,C2空间群,其中α=10.286(3)(A),b=4.6163(11)(A),c=17.111(4)(A);β=104.995(4)°.通过L-谷氨酸-5-甲酯与MgCl2·6H2O和Ca(OH)2反应,分别合成得到了相应的金属化合物.用比色法测试了L-谷氨酸-5-甲酯对三磷酸腺苷二钠分解的催化活性,结果表明:L-谷氨酸-5-甲酯合镁和L-谷氨酸-5-甲酯合钙对三磷酸腺苷二钠的分解具有较好的活性.     

聚L-谷氨酸修饰电极的制备及其对扑热息痛的测定

用电聚合法制备了聚L-谷氨酸修饰玻碳电极,研究了扑热息痛在聚L-谷氨酸修饰电极上的电化学行为,建立了测定扑热息痛的新方法.结果表明,在pH 7.0的磷酸盐缓冲溶液中,利用差分脉冲伏安法测定扑热息痛,在0.1～140μmol/L浓度范围内其浓度与氧化峰电流呈良好的线性关系,相关系数为0.998.信噪比为3时,扑热息痛检出限为0.03μmol/L.将该方法用于扑热息痛药片分析,回收率为95.2%～104.8%.     

谷氨酸酶电极的研制

将产生谷氨酸脱羧酶(GDC)的大肠杆菌菌株(E,Coli.,AS.505),在37℃培养,所得细胞经抽提得到GDC粗品,将它固定于海藻酸钠上,配合CO_2选择性电极,制得谷氨酸酶电极。它具有下列特性:(1)电极对谷氨酸的线性响应浓度范围是1.0×10~(-3)—0.5tmol/L(8.3—6300mg)谷氨酸/L;(2)电极动态响应时间1分钟,即可达约90%响应值,静态响应时间约10分钟;(3)电极连续测定六十次以上仍有响应;(4)除L-赖氨酸及L-谷氨酰胺外,其余氨基酸均不干扰电极对谷氨酸的测定;(5)电极具较高的重演性。     

应用RSM法优化L-谷氨酸发酵培养基

采用响应面法（RSM）对L-谷氨酸发酵培养基中的成分玉米浆、豆饼水解液、硫酸镁进行优化．采用多元二次回归方程拟合3种因素与L-谷氨酸产量的函数关系,得到了最适发酵的培养基。在优化培养条件下,发酵液中L-谷氨酸的产量由83．3g／L提高到96．8g／L,比原产量提高了16．1％。     

用二氧化碳电极测定霉菌537蛋白酶的活性

在霉菌５３７蛋白酶的作用下，酷蛋白发生水解，生成酪氨酸和谷氨酸等组成该蛋白的氨基酸，加入Ｌ－谷氨酸脱羧酶使谷氨酸发生脱羧反应，会释放出ＣＯ２，后者可用ＣＯ２电极进行测定，从而可间接地算出５３７蛋白酶的活性，在蛋白酶活性为２０００－１０００单位范围内，电位的变化值与活性呈现良好的线性关系。     

L-谷氨酸-5-乙酯及其金属配合物的合成、表征和催化活性

以L-谷氨酸为原料合成了L-谷氨酸-5-乙酯,并对其进行了X-射线单晶衍射测定.测量结果表明:L-谷氨酸-5-乙酯属单斜晶系,P2(1)空间群,其中a=9.691(3),b=5.2631(17),c=17.297(6);β=90.752(5)°.通过L-谷氨酸-5-乙酯分别与MgCl2.6H2O和Ca(OH)2反应,合成得到了Mg(II)和Ca(II)的金属配合物.比色法测试结果表明:L-谷氨酸-5-乙酯与镁和钙形成的配合物对三磷酸腺苷二钠的分解反应具有较好的活性.     

两种聚多肽材料的合成及其结晶结构研究

本文利用L-谷氨酸苄酯和L-赖氨酸苄酯分别与三光气反应合成N-羧基- L-谷氨酸g-苄酯环内酸酐(NCA)和N-羧基-L-赖氨酸g-苄酯环内酸酐,用三乙胺作为引发剂,引发NCA进行开环聚合,合成了聚谷氨酸苄酯与聚谷氨酸赖氨酸苄酯共聚物。利用核磁共振仪 (1H-NMR)、傅里叶变换红外光谱(FTIR)、凝胶渗透色谱(GPC)及X射线衍射仪(1D-WAXD)等方法对单体、聚合物的分子结构以及结晶性能进行了表征。     

柠檬酸钠对L-谷氨酸发酵代谢流迁移的影响

为更全面深入地理解细胞内谷氨酸代谢的调控机制,以黄色短杆菌GDK-9为供试菌株,应用MATLAB软件和代谢流分析方法,定量研究了添加柠檬酸钠后L-谷氨酸发酵中后期胞内的代谢流迁移.在L-谷氨酸发酵中后期添加3.0 g/L柠檬酸钠后.合成副产物L-丙氨酸和乳酸的代谢流量明显减少,分别降低了18.7%和27.4%,EMP途径和乙醛酸循环的代谢流分别减少了0.88和2.12,HMP途径的代谢流增加了0.88,而L-谷氨酸生物合成的代谢流从73.59增长至76.47,较未添加前提高了3.9%.添加柠檬酸钠能使关键节点发生代谢流迁移,提高L-谷氨酸合成中心代谢途径的代谢流量.     

L-谷氨酸-5-甲酯金属铜化合物的合成、表征及生物活性

通过L-谷氨酸-5-甲酯与Cu（CH3COO）2.H2O反应,合成了相应的金属铜化合物[Cu（C6H10NO4）2].对L-谷氨酸-5-甲酯金属铜化合物的晶体进行了X-射线单晶衍射测定.结果表明：L-谷氨酸-5-甲酯金属铜化合物属单斜晶系,P2（1）空间群,其中a=9.5883（19）,b=5.1521（10）,c=15.562（3）;β=98.65（3）°.抗菌筛选数据表明,L-谷氨酸-5-甲酯金属铜化合物对枯草芽胞杆菌具有较好的抑制作用.     

氨基酸分析仪法快速检测土鳖虫中谷氨酸含量

采用氨基酸分析仪建立了土鳖虫中谷氨酸含量的检测方法，比较不同浓度的盐酸以及不同料液比、提取时间对土鳖虫中谷氨酸提取效果的影响。结果表明，土鳖虫中谷氨酸的最佳提取工艺为6 mol/L 的盐酸消解，料液比1:1（mg/mL），水解时间22 h，建立的谷氨酸分析仪法回收率为99.2%，精密度试验相对标准偏差为0.19%，不同地区土鳖虫中谷氨酸质量分数存在较明显差异，范围为1.068%~1.149%。该方法重现性好、快速高效、操作简便，适用于土鳖虫中氨基酸含量的检测，可为其质量控制及资源深入开发提供技术支持。     

Positive feedback of glutamate exocytosis by metabotropic presynaptic receptor stimulation.

Glutamate is important in several forms of synaptic plasticity such as long-term potentiation, and in neuronal cell degeneration. Glutamate activates several types of receptors, including a metabotropic receptor that is sensitive to trans-1-amino-cyclopenthyl-1,3-dicarboxylate, coupled to G protein(s) and linked to inositol phospholipid metabolism. The activation of the metabotropic receptor in neurons generates inositol 1,4,5-trisphosphate, which causes the release of Ca2+ from intracellular stores and diacylglycerol, which activates protein kinase C. In nerve terminals, the activation of presynaptic protein kinase C with phorbol esters enhances glutamate release. But the presynaptic receptor involved in this protein kinase C-mediated increase in the release of glutamate has not yet been identified. Here we demonstrate the presence of a presynaptic glutamate receptor of the metabotropic type that mediates an enhancement of glutamate exocytosis in cerebrocortical nerve terminals. Interestingly, this potentiation of glutamate release is observed only in the presence of arachidonic acid, which may reflect that this positive feedback control of glutamate exocytosis operates in concert with other pre- or post-synaptic events of the glutamatergic neurotransmission that generate arachidonic acid. This presynaptic glutamate receptor may have a physiological role in the maintenance of long-term potentiation where there is an increase in glutamate release mediated by postsynaptically generated arachidonic acid.     

Arachidonic acid induces a prolonged inhibition of glutamate uptake into glial cells

Activation of NMDA (N-methyl-D-aspartate) receptors by neurotransmitter glutamate stimulates phospholipase A2 to release arachidonic acid. This second messenger facilitates long-term potentiation of glutamatergic synapses in the hippocampus, possibly by blocking glutamate uptake. We have studied the effect of arachidonic acid on glutamate uptake into glial cells using the whole-cell patch-clamp technique to monitor the uptake electrically. Micromolar levels of arachidonic acid inhibit glutamate uptake, mainly by reducing the maximum uptake rate with only small effects on the affinity for external glutamate and sodium. On removal of arachidonic acid a rapid (5 minutes) phase of partial recovery is followed by a maintained suppression of uptake lasting at least 20 minutes. Surprisingly, the action of arachidonic acid is unaffected by cyclo-oxygenase or lipoxygenase inhibitors suggesting that it inhibits uptake directly, possibly by increasing membrane fluidity. As blockade of phospholipase A2 prevents the induction of long-term potentiation (LTP), inhibition of glutamate uptake by arachidonic acid may contribute to the increase of synaptic gain that occurs in LTP. During anoxia, release of arachidonic acid could severely compromise glutamate uptake and thus contribute to neuronal death.     

谷氨酸的N-酰化反应

在催化剂条件下，用脂肪酰氯与谷氨酸缩合法生产N-酰基谷氨酸钠，通过选择酰化剂及改变酰化剂用量等条件合成了一系列N-酰基谷氨酸钠缩合物，这些缩合物经酸化结晶再用碳酸钠中和成N-酰基谷氨酸钠产品。     

GABAA responses in hippocampal neurons are potentiated by glutamate

In the mammalian cortex, glutamate and gamma-aminobutyric acid (GABA) are the principal transmitters mediating excitatory and inhibitory synaptic events. Glutamate activates cation conductances that lead to membrane depolarization whereas GABA controls chloride conductances that produce hyperpolarization. Here we report that the GABAA-activated conductance in hippocampal pyramidal cells is enhanced by glutamate at concentrations below that required for its excitatory action. The GABA-potentiating effect can be induced, with comparable potency, by several glutamate analogues such as quisqualate, N-methyl-D-aspartate (NMDA), kainate and, surprisingly, by D-2-amino-5-phosphonovalerate (APV), an antagonist for NMDA receptors. Data from dose-response curves show that glutamate enhances the GABAA conductance without significantly changing GABA binding affinity. The low concentration of glutamate needed to enhance GABAA responses raises the possibility that glutamate modulates the strength of GABA-mediated transmission in the cortex.     

脯氨酸的代谢

本文简要地介绍了脯氨酸的代谢情况。脯氨酸是由谷氨酸或乌氨酸合成的,分解为谷氨酸、有机酸和CO_2。P5C在脯氨酸代谢中起中心作用。脯氨酸还向蛋白质掺入,并被转化成羟脯氨酸。     

产γ-氨基丁酸乳酸菌的筛选

从多种酸菜水中分离筛选出乳酸菌,利用乳酸菌将谷氨酸转化为GABA的脱羧作用,通过混合酸碱指示剂颜色变化,直观判断谷氨酸脱羧酶（GAD）活性,进而筛选出产GABA乳酸菌菌株BL2,并对其进行初步鉴定;同时,采用纸层析法进行定性分析,确定菌株BL2可将谷氨酸钠转化生成GABA.     

谷氨酸生产菌的诱变育种

经化学诱变,通过改变谷氨酸棒杆菌B1的代谢途径,筛选出以琥珀酰CoA和乙醛酸为碳源的营养缺陷型,该突变菌株B4的产酸率和转化率分别比出发菌株高11.1%和8.7%.     

Modulation of the neuronal glutamate transporter EAAC1 by the interacting protein GTRAP3-18

Excitatory amino-acid carrier 1 (EAAC1) is a high-affinity Na+-dependent L-glutamate/D,L-aspartate cell-membrane transport protein. It is expressed in brain as well as several non-nervous tissues. In brain, EAAC1 is the primary neuronal glutamate transporter. It has a polarized distribution in cells and mainly functions perisynaptically to transport glutamate from the extracellular environment. In the kidney it is involved in renal acidic amino-acid re-absorption and amino-acid metabolism. Here we describe the identification and characterization of an EAAC1-associated protein, GTRAP3-18. Like EAAC1, GTRAP3-18 is expressed in numerous tissues. It localizes to the cell membrane and cytoplasm, and specifically interacts with carboxy-terminal intracellular domain of EAAC1. Increasing the expression of GTRAP3-18 in cells reduces EAAC1-mediated glutamate transport by lowering substrate affinity. The expression of GTRAP3-18 can be upregulated by retinoic acid, which results in a specific reduction of EAAC1-mediated glutamate transport. These studies show that glutamate transport proteins can be regulated potently and that GTRAP can modulate the transport functions ascribed to EAAC1. GTRAP3-18 may be important in regulating the metabolic function of EAAC1.     

JWA,a novel microtubule-associated protein,regulates homeostasis of intracellular amino acids in PC12 cells

Microtubules are long, stiff polymers that extendthroughout the cytoplasm and govern the location of membrane-bounded organelles and other cell components.The building block of a microtubule is the tubulin subunit, a heterodimer of a- and b-tubulin. Both of these 50 kDmonomers are found in all eukaryotes, and their se-quences are highly conserved. The bulk of cellular tubulin is cytoplasmic, but a significant fraction is embedded in, or firmly associated with the plasma membrane and other memb…