金黄仓鼠视觉中枢的甘氨酸免疫阳性神经元

用免疫细胞化学方法研究了甘氨酸在金黄仓鼠视觉中枢的分布特征, 并应用统计学方法进行了定量分析.结果表明：在视皮层中, 除了Ⅰ层以外, 甘氨酸免疫阳性神经元分布在其他各层内, 其平均密度为1 046/mm²,占视皮层细胞总数的23.9％.上丘浅灰层及视觉层甘氨酸免疫阳性神经元平均密度为750/mm²,占该层细胞总数的19.5％.外膝体中甘氨酸免疫阳性神经元密度较低.甘氨酸免疫阳性神经元包括不同类型的细胞.     

甘氨酸及其衍生物的抗菌作用

本文讨论甘氨酸、甘氨酸盐、甘氨酸高级脂肪醇的酯以及其它甘氨酸衍生物的抗菌作用。     

富含甘氨酸抗菌肽的研究进展

抗菌肽是机体先天免疫的重要组成部分,种类繁多。其中富含甘氨酸抗菌肽广泛存在于多种生物体,具有广谱抗菌活性,并且在药物治疗、农业、食品业等方面已经取得一定成绩,该文根据近年抗菌肽研究成果,综述了富含甘氨酸抗菌肽的分类、作用机制、存在的问题和应用前景。     

甘氨酸

<正> 甘氨酸(Glycine)化学名为α-氨基乙酸,是结构最简单的氨基酸,它是组成天然蛋白质的氨基酸之一,它在医药、食品、化工和农业上有广泛的应用。世界上甘氨酸的产量仅次于谷氨酸钠、蛋氨酸和赖氨酸居第四位,产量年增长率为2～3％,1985年产量将达4000吨~(〔1〕),日本是主要甘氨酸的生     

甘氨酸和谷氨酸与钼配施对生菜品质的影响

以美国大速不结球生菜为材料,采用水培法研究了单一甘氨酸和谷氨酸分别替代营养液中20%硝态氮处理以及配合施加钼(0.002 mmol·L-1)处理对植株叶片鲜重和营养品质的影响.结果显示:(1)单一甘氨酸、谷氨酸替代处理培养12～16d,均可显著提高生菜叶片的鲜重和品质,其中甘氨酸对降低叶片硝酸盐含量、提高游离氨基酸和维生素C含量的效果好于谷氨酸,而谷氨酸促进生长和提高可溶性蛋白质、可溶性糖和叶绿素含量的效果好于甘氨酸.(2)甘氨酸与钼配合施用培养8～16 d的叶片鲜重显著高于单独甘氨酸替代处理,而谷氨酸与钼配合施用处理叶片鲜重与单独谷氨酸替代处理无显著差异;钼的配合施用进一步提高了甘氨酸、谷氨酸改善品质的作用效果,其叶片游离氨基酸、可溶性蛋白质、维生素C、可溶性糖和叶绿素含量显著提高,而硝酸盐含量显著降低,但甘氨酸与钼配合施用效果较好.研究表明,甘氨酸、谷氨酸均可作为生菜生长的氮源,并与钼配合施用对提高生菜产量和品质具有协同配合效应,且以甘氨酸与钼配施12 d效果较好.     

甘氨酸

<正> 甘氨酸(Glycine)化学名为α-氨基乙酸,是结构最简单的氨基酸,它是组成天然蛋白质的氨基酸之一,它在医药、食品、化工和农业上有广泛的应用。世界上甘氨酸的产量仅次于谷氨酸钠、蛋氨酸和赖氨酸居第四位,产量年增长率为2～3％,1985年产量将达4000吨~(〔1〕),日本是主要甘氨酸的生     

嗜盐菌中甘氨酸甜菜碱的合成途径及其生物学功能

在嗜盐菌长期的盐适应或短期的盐胁迫过程中,甘氨酸甜菜碱(又名三甲基甘氨酸,N,N,N-trimethylglycine)发挥着极为重要的作用。甘氨酸甜菜碱在嗜盐菌中的生物合成有2种途径:胆碱氧化途径和甘氨酸甲基化途径。前者以胆碱为底物,由胆碱脱氢酶(cholinedehydrogenase,BetA)和甜菜碱乙醛脱氢酶(betaine aldehyde dehydrogenase,BetB)经2次氧化生成甜菜碱;后者以甘氨酸作为底物,由甘氨酸肌醇甲基转移酶(glycine sarcosine N-methyltransferase,GSMT)和肌氨酸二甲基甘氨酸甲基转移酶(sarcosine dimethylglycine N-methyltransferase,SDMT)经3次N-甲基化生成甜菜碱。目前在JGI-IMG和EZBioCloud数据库中公布了134株嗜盐菌标准菌株的全基因组序列。其中,约56.0%的嗜盐细菌和约39.6%的嗜盐古菌拥有胆碱氧化途径所需的2个基因;约9.7%的嗜盐细菌和约0.7%的嗜盐古菌携带甲基化途径所需的2个基因。其中,8株嗜盐细菌同时拥有胆碱氧化途径和甘氨酸甲基化途径所需的全部基因。甘氨酸甜菜碱生物合成基因在典型微生物菌株或经济作物中的表达可以提高其耐盐抗逆能力,这种独特的优势已经引起科学家们强烈的兴趣,相信未来,嗜盐菌中甘氨酸甜菜碱生物合成领域内的科学理论和技术应用会有重大的突破。     

不同晶型甘氨酸在水中溶解度的测定与关联

不同晶型甘氨酸溶解度的测定对研究甘氨酸结晶及多晶型现象具有重要意义。采用激光动态法测定了15~80℃范围内α型和γ型甘氨酸在纯水中的溶解度数据,并且采用Apelb lat溶解度经验方程对实验数据进行了关联,回归了溶解度经验方程的参数,关联效果令人满意。实验结果表明,在水中α和γ甘氨酸溶解度均随温度升高而变大;在相同温度下,热力学亚稳的α型甘氨酸比稳态的γ型甘氨酸溶解度大。     

发酵法制取谷氨酸

由发酵法制取谷氨酸时,通过添加一个或多个N-甲基甘氨酸,N、N-二甲基甘氨酸,N、N、N-三甲基甘氨酸和三甲基铵于培养基中,显著地增加了L—     

甘氨酸对缺血缺氧心肌细胞能量代谢的影响

目的:明确甘氨酸对缺血缺氧心肌细胞具有保护作用.方法:建立心肌细胞缺血缺氧模型,施加甘氨酸干预,应用高效液相色谱观察心肌细胞ATP、ADP、AMP含量变化及ATP/ADP比值.结果:模拟缺血缺氧1 h后开始心肌细胞ATP含量较正常组明显降低(P＜0.01),而ADP、AMP含量与ATP变化相反,ATP/ADP比值较正常组也明显降低(P＜0.01);甘氨酸干预复合缺血缺氧后,心肌细胞ATP含量及ATP/ADP比值较单纯缺血缺氧组显著降低(P＜0.01),而ADP、AMP含量明显升高(P＜0.01).结论:甘氨酸可以明显改善缺血缺氧心肌细胞的能量储备,发挥其保护效应.     

Regulation of the glycine cleavage system in the isolated perfused rat liver

The catabolism of glycine in the isolated perfused rat liver was investigated by measuring the production of 14CO2 from [1-14C]- and [2-14C]glycine. Production of 14CO2 from [1-14C]glycine was maximal as the perfusate glycine concentration approached 10 mM and exhibited a maximal activity of 125 nmol of 14CO2 X g-1 X min-1 and an apparent Km of approximately 2 mM. Production of 14CO2 from [2-14C]glycine was much lower, approaching a maximal activity of approximately 40 nmol of 14CO2 X g-1 X min-1 at a perfusate glycine concentration of 10 mM, with an apparent Km of approximately 2.5 mM. Washout kinetic experiments with [1-14C]glycine exhibited a single half-time of 14CO2 disappearance, indicating one metabolic pool from which the observed 14CO2 production is derived. These results indicate that the glycine cleavage system is the predominant catabolic fate of glycine in the perfused rat liver and that production of 14CO2 from [1-14C]glycine is an effective monitor of metabolic flux through this system. Metabolic flux through the glycine cleavage system in the perfused rat liver was inhibited by processes which lead to reduction of the mitochondrial NAD(H) redox couple. Infusion of beta-hydroxybutyrate or octanoate inhibited 14CO2 production from [1-14C]glycine by 33 and 50%, respectively. Alternatively, infusion of acetoacetate stimulated glycine decarboxylation slightly and completely reversed the inhibition of 14CO2 production by octanoate. Metabolic conditions which are known to cause a large consumption of mitochondrial NADPH (e.g. ureogenesis from ammonia) stimulated glycine decarboxylation by the perfused rat liver. Infusion of pyruvate and ammonium chloride stimulated production of 14CO2 from [1-14C]glycine more than 2-fold. Lactate plus ammonium chloride was equally as effective in stimulating glycine decarboxylation by the perfused rat liver, while alanine plus ammonium chloride was ineffective in stimulating 14CO2 production.     

Glycine metabolism by Pseudomonas aeruginosa: hydrogen cyanide biosynthesis.

Hydrogen cyanide (HCN) production by Pseudomonas aeruginosa in a synthetic medium is stimulated by the presence of glycine. Methionine enhances this stimulation but will not substitute for glycine as a stimulator of cyanogenesis. Threonine and phenylalanine are effective substitutes for glycine in the stimulation of HCN production. Glycine, threonine, and serine are good radioisotope precursors of HCN, but methionine and phenylalanine are not. Cell extracts of P. aeruginosa convert [14C]threonine to [14C]glycine. H14CN is produced with low dilution of label from either [1-14C]glycine or [2-14C]glycine, indicating a randomization of label either in the primary or secondary metabolism of glycine. When whole cells were fed [1,2-14C]glycine, cyanide and bicarbonate were the only radioactive extracellular products observed.     

A two-stage glycine supplementation strategy enhances the extracellular expression of sortase A in Escherichia coli

Sortase A (SrtA) is a transpeptidase widely used in protein engineering. In this study, the enhancement of the extracellular expression of SrtA in Escherichia coli was investigated using a combined strategy based on the PelB signal peptide and chemical additives. First, glycine was identified to be the best additive for promoting the release of SrtA from the periplasm to the medium. Then, the effect of glycine concentration on cell growth and SrtA production was investigated, and a two-stage supplementation strategy was developed in order to control the impairment of cell growth and to achieve the maximum production of secretory SrtA. The results showed that when 0.5% glycine was added to the medium at the beginning of cell growth and 1% glycine was added at the end of the exponential phase, the extracellular yield of SrtA was 228.0 mg/L and the enzyme activity was 100.4 U/mL at the end of fermentation; these values were 5.3- and 8.6-fold higher, respectively, than those attained in the control culture without any additives. This result represents the highest yield of extracellular SrtA ever reported and demonstrates a promising process for the production of SrtA for large-scale industrial application.     

Glycine receptor activation regulates short-term plasticity in CA1 area of hippocampal slices of rats

Functional glycine receptors (GlyRs) are enriched in the hippocampus, but their roles in synaptic transmission are unclear. In this study, we examined the effect of GlyR activation on paired-pulse stimulation of the whole-cell postsynaptic currents (PSCs) in the Schaffer-CA1 synapses in rat hippocampal slices. Bath application of glycine reduced the amplitude of PSCs, accompanied by an increase in holding current and resting conductance. Moreover, glycine application increased the paired-pulse ratio (PPR) of PSCs significantly, an effect largely abolished by the GlyR specific antagonist strychnine. Interestingly, glycine application had no significant effect on either the amplitude or the PPR of excitatory postsynaptic currents (EPSCs). Our findings suggest that GlyR activation regulates hippocampal short-term plasticity by altering GABAergic neurotransmission.     

A Sensitive and Simple Method for the Determination of Fatty Acid Hydroperoxides with Horseradish Peroxidase

Glycine, glycylglycine, glycine methyl ester and glycine ethyl ester were found to be effective for the production and release of γ-galactosidase by Escherichia coli. Addition of an appropriate concentration of glycine and glycylglycine to the culture increased total enzyme production 6 to 7-fold and extracellular enzyme production over 240-fold at 24 hr cultivation. The enzyme synthesis was stimulated even at the exponential period of growth, and 93% of enzyme was found in the culture fluid at 24 hr cultivation on addition of 1.2% glycine. A large amount of protein was also accumulated in the culture fluid. A micrograph showed glycine gave swollen and irregular cells, indicating that the cell surface was altered. Various amino acid analogues and some antibiotics had a small or no effect on the production and release of the enzyme as compared with glycine. Polypeptone or brain heart infusion was needed as a nitrogen source for efficient production of the enzyme.     

Activation of N-Methyl-d-aspartate (NMDA) Receptors in the Dorsal Vagal Complex Lowers Glucose Production

Diabetes is characterized by hyperglycemia due partly to increased hepatic glucose production. The hypothalamus regulates hepatic glucose production in rodents. However, it is currently unknown whether other regions of the brain are sufficient in glucose production regulation. The N-methyl-d-aspartate (NMDA) receptor is composed of NR1 and NR2 subunits, which are activated by co-agonist glycine and glutamate or aspartate, respectively. Here we report that direct administration of either co-agonist glycine or NMDA into the dorsal vagal complex (DVC), targeting the nucleus of the solitary tract, lowered glucose production in vivo. Direct infusion of the NMDA receptor blocker MK-801 into the DVC negated the metabolic effect of glycine. To evaluate whether NR1 subunit of the NMDA receptor mediates the effect of glycine, NR1 in the DVC was inhibited by DVC NR1 antagonist 7-chlorokynurenic acid or DVC shRNA-NR1. Pharmacological and molecular inhibition of DVC NR1 negated the metabolic effect of glycine. To evaluate whether the NMDA receptors mediate the effects of NR2 agonist NMDA, DVC NMDA receptors were inhibited by antagonist d-2-amino-5-phosphonovaleric acid (d-APV). DVC d-APV fully negated the ability of DVC NMDA to lower glucose production. Finally, hepatic vagotomy negated the DVC glycine ability to lower glucose production. These findings demonstrate that activation of NR1 and NR2 subunits of the NMDA receptors in the DVC is sufficient to trigger a brain-liver axis to lower glucose production, and suggest that DVC NMDA receptors serve as a therapeutic target for diabetes and obesity.     

Mechanisms of interactions between glycine- and GABA-mediated responses in spinal cord neurons

The interactions of GABA- and glycine-mediated responses have been analyzed, the whole cell patch-clamp method being used. The response induced by co-application of glycine and GABA was a lesser one than the sum of responses induced by applying two transmitters separately. The molecular mechanisms underlying this effect have been determined. Due to applications of high concentrations of neurotransmitters it was revealed that GABA could activate glycine receptors in frog spinal motoneurons with relatively high efficiency (EC50 = 1.2 mM). The sequential application of neurotransmitters showed that even a single application of glycine could significantly boost the "run-down" of the GABA-mediated current, suggesting that there was a strong phosphorylation-dependent mechanism of GABAa-receptors inhibition. These mechanisms are likely to take place in frog spinal motoneurons when GABA and glycine are co-released from the same synaptic terminal.     

Modulation of endogenous levels of some key organic metabolites by exogenous application of glycine betaine in drought stressed plants of sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.)

The present study was conducted to examine the changes in some key metabolites in drought-stressed sunflower plants supplied with glycine betaine externally. Imposition of drought stress at the vegetative or reproductive growth stages decreased the plant dry matter production and increased the accumulation of organic solutes (glycine betaine, proline, soluble proteins, free amino acids and soluble sugars) in two sunflower lines, i.e., Glushan-98 and Suncross. In general, decrease in dry matter production and increase in the endogenous levels of organic solutes, were more pronounced when drought stress applied at the vegetative stage than at the reproductive stage. Glycine betaine applied as a pre-sowing seed treatment was not found to be effective in reducing the negative effects of drought stress in sunflower plants. Foliar application of GB further enhanced the leaf endogenous levels of GB, soluble proteins and total soluble sugars in drought stressed plants without exerting any negative effects on other osmotica. However, this GB-induced increase in endogenous levels of organic solutes was found to be not associated with plant dry matter production under stress conditions.     

Cellular Choline and Glycine Betaine Pools Impact Osmoprotection and Phospholipase C Production in Pseudomonas aeruginosa

Choline is abundantly produced by eukaryotes and plays an important role as a precursor of the osmoprotectant glycine betaine. In Pseudomonas aeruginosa, glycine betaine has additional roles as a nutrient source and an inducer of the hemolytic phospholipase C, PlcH. The multiple functions for glycine betaine suggested that the cytoplasmic pool of glycine betaine is regulated in P. aeruginosa. We used (13)C nuclear magnetic resonance ((13)C-NMR) to demonstrate that P. aeruginosa maintains both choline and glycine betaine pools under a variety of conditions, in contrast to the transient glycine betaine pool reported for most bacteria. We were able to experimentally manipulate the choline and glycine betaine pools by overexpression of the cognate catabolic genes. Depletion of either the choline or glycine betaine pool reduced phospholipase production, a result unexpected for choline depletion. Depletion of the glycine betaine pool, but not the choline pool, inhibited growth under conditions of high salt with glucose as the primary carbon source. Depletion of the choline pool inhibited growth under high-salt conditions with choline as the sole carbon source, suggesting a role for the choline pool under these conditions. Here we have described the presence of a choline pool in P. aeruginosa and other pseudomonads that, with the glycine betaine pool, regulates osmoprotection and phospholipase production and impacts growth under high-salt conditions. These findings suggest that the levels of both pools are actively maintained and that perturbation of either pool impacts P. aeruginosa physiology.     

Reversible lysine acetylation regulates activity of human glycine N-acyltransferase-like 2 (hGLYATL2): implications for production of glycine-conjugated signaling molecules

Lysine acetylation is a major post-translational modification of proteins and regulates many physiological processes such as metabolism, cell migration, aging, and inflammation. Proteomic studies have identified numerous lysine-acetylated proteins in human and mouse models (Kim, S. C., Sprung, R., Chen, Y., Xu, Y., Ball, H., Pei, J., Cheng, T., Kho, Y., Xiao, H., Xiao, L., Grishin, N. V., White, M., Yang, X. J., and Zhao, Y. (2006) Mol. Cell 23, 607-618). One family of proteins identified in this study was the murine glycine N-acyltransferase (GLYAT) enzymes, which are acetylated on lysine 19. Lysine 19 is a conserved residue in human glycine N-acyltransferase-like 2 (hGLYATL2) and in several other species, showing that this residue may be important for enzyme function. Mutation of lysine 19 in recombinant hGLYATL2 to glutamine (K19Q) and arginine (K19R) resulted in a 50-80% lower production of N-oleoyl glycine and N-arachidonoylglycine, indicating that lysine 19 is important for enzyme function. LC/MS/MS confirmed that Lys-19 is not acetylated in wild-type hGLYATL2, indicating that Lys-19 requires to be deacetylated for full activity. The hGLYATL2 enzyme conjugates medium- and long-chain saturated and unsaturated acyl-CoA esters to glycine, resulting in the production of N-oleoyl glycine and also N-arachidonoyl glycine. N-Oleoyl glycine and N-arachidonoyl glycine are structurally and functionally related to endocannabinoids and have been identified as signaling molecules that regulate functions like the perception of pain and body temperature and also have anti-inflammatory properties. In conclusion, acetylation of lysine(s) in hGLYATL2 regulates the enzyme activity, thus linking post-translational modification of proteins with the production of biological signaling molecules, the N-acyl glycines.