Tryptophanase-catalysed degradation of D-tryptophan in highly concentrated diammonium hydrogen phosphate solution

Summary Tryptophanase is and is perfectly inert to D-tryptophan under ordinary conditions. However, activity that can degrade D-tryptophan into indole is observed when tryptophanase is in highly concentrated diammoniumhydrogen phosphate solution. The reaction has been so far unknown in tryptophanase metabolic pathways. Here we report the characteristic of the reaction. We also discuss its significance in relation to selection of an amino acid optical isomer from a racemic mixture.Abbreviations AP diammoniumhydrogen phosphate - TPase tryptophanase - L-Trp L-tryptophan - D-Trp D-tryptophan - PLP pyridoxal 5-phosphate     

Transcriptional profiling of wine yeast in fermenting grape juice: regulatory effect of diammonium phosphate

The nitrogen composition of grape musts affects fermentation kinetics and production of aroma and spoilage compounds in wine. It is common practice in wineries to supplement grape musts with diammonium phosphate (DAP) to prevent nitrogen-related fermentation problems. Laboratory strains of Saccharomyces cerevisiae preferentially use rich nitrogen sources, such as ammonia, over poor nitrogen sources. We used global gene expression analysis to monitor the effect of DAP addition on gene expression patterns in wine yeast in fermenting Riesling grape must. The expression of 350 genes in the commercial wine yeast strain VIN13 was affected; 185 genes were down-regulated and 165 genes were up-regulated in response to DAP. Genes that were down-regulated encode small molecule transporters and nitrogen catabolic enzymes, including those linked to the production of urea, a precursor of ethyl carbamate in wine. Genes involved in amino acid metabolism, assimilation of sulfate, de novo purine biosynthesis, tetrahydrofolate one-carbon metabolism, and protein synthesis were up-regulated. The expression level of 86 orphan genes was also affected by DAP.     

Food consumption of Sarotherodon mossambicus (Trewaves) exposed to sublethal concentration of diammonium phosphate

S. mossambicus was exposed to toxic and sublethal concentrations of the fertilizer diammonium phosphate (0.2 to 1.0 g l^–1). Mortality, food utilization and growth were studied. At a concentration of 0.6 g l^–1 DAP, 100% mortality was observed within 96 h; no mortality occurred at 0.5 g l^–1; LC50 was 0.55 g l^–1. Rearing the fish in increasing sublethal concentrations of DAP, it was found that the feeding rate decreased from 25.4 mg g^–1 fish^–1 d^–1 (fish reared in DAP-free water) to 10.1 mg g^–1 d^–1 at the highest sublethal concentration (0.5 g l^–1). Growth rate was drastically reduced. At high sublethal concentrations of DAP, the fish lost reserve energy, in addition to the energy obtained from food intake for survival, as a result of increased swimming activity and opercular beats.     

The timing of diammonium phosphate supplementation of wine must affects subsequent H2S release during fermentation

Aims:  The aim of this study was to evaluate the impact of supplementation by diammonium phosphate (DAP) on hydrogen sulfide (H₂S) production, when DAP given either prior to fermentation or during the early stationary growth phase of yeast. Methods and Results:  Three contrasting Saccharomyces cerevisiae wine strains were used to ferment synthetic grape juice (GJ) containing 67 mg l^?1 of initial yeast assimilable nitrogen (YAN), supplied either as DAP or as mixture of amino acids. Sufficient DAP was added either prior to or 72 h after the initiation of fermentation to achieve a final YAN concentration of 267 mg l^?1. Supplementation prior to fermentation stimulated H₂S production. The results obtained in model solutions were validated using natural GJ. Conclusion:  The timing of DAP supplementation is critical for ensuring that fermentation proceeds without excessive release of H₂S. Significance and Impact of the Study:  This result has important implications for the wine‐making industry, because it highlights the value of determining the initial nitrogen level of a GJ. It raises awareness of the dependence of wine quality on the correct timing of DAP supplementation.     

甘南高寒草甸土壤纤毛虫对磷酸氢二铵添加的响应

为研究磷酸氢二铵(DAP)添加对土壤纤毛虫群落结构的影响,于2012年4月在甘南高寒草甸选取典型样地,在0～120 g·m^-2浓度区间内设置5个添加水平,采用“非淹没培养皿法”、活体观察法和“3级10倍环式稀释法”测定土壤纤毛虫物种数和密度,同时测定了土壤相关环境因子(含水量、pH值、总氮、总磷、有机碳).共获得土壤纤毛虫129种,隶属9纲17目31科46属.对照组的土壤纤毛虫物种数和物种多样性指数均大于施肥处理,且随着施肥量的增大,土壤纤毛虫物种数减少,物种多样性减小,但其密度随施肥量的增大而增加.对照土壤纤毛虫优势类群为刺钩目,随着施肥量的增大,土壤纤毛虫优势类群更新为肾形目.土壤纤毛虫群落结构和环境因子的冗余分析表明,总磷、土壤温度和含水量是影响甘南高寒草甸土壤纤毛虫群落分布的关键环境因子.     

Metabolic profiling reveals the protective effect of diammonium glycyrrhizinate on acute hepatic injury induced by carbon tetrachloride

Diammonium glycyrrhizinate (DG), a constitutent of Glycyrrhiza uralensis, has a protective effect on hepatic injury, hepatisis and cirrhosis. To date, the mechanism has been poorly understood, especially at the metabolic level. A metabolomic profiling study was performed to characterize the carbon tetrachloride (CCl₄) induced global metabolic alteration and the protective effects of DG in Sprague-Dawley rats. Urinary and hepatic tissue metabolic profiling revealed that CCl₄ perturbed the amino acid metabolism (alanine, glycine, leucine), tricarboxylic acid cycle (citrate), lipid metabolism (unsaturated fatty acids) and gut microbiota related metabolites. Our results also indicated that DG was able to attenuate CCl₄ perturbed metabolic pathways and ameliorated biochemical markers of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and Total cholesterol (TCHO). This global metabolomic approach also revealed full metabolic recovery takes longer than apparent and conventional histological and biochemical markers.     

甘草酸二铵脂质配位体对非酒精性脂肪肝大鼠白细胞浸润的影响

目的研究甘草酸二铵脂质配位体(DGLL)对非酒精性脂肪肝(NAFLD)大鼠白细胞浸润的影响及机制。方法用高脂乳剂灌胃诱导大鼠NAFLD模型并给予DGLL干预,6周后观察肝脏组织中髓过氧化物酶(MPO)的表达,酶标仪法测定肝脏组织MPO活性的变化,流式细胞技术测定外周血白细胞粘附分子表达的变化,Western blot技术检测肝脏组织内皮细胞间粘附分子-1(ICAM-1)的表达水平。结果与高脂模型组相比,DGLL能明显降低NAFLD大鼠肝脏组织中白细胞MPO的表达和活化,下调大鼠外周血中单核细胞和粒细胞粘附分子的表达,同时显著地抑制肝脏组织中内皮细胞ICAM-1的表达。结论 DGLL能显著降低高脂饮食诱导的NAFLD大鼠肝脏组织中白细胞的活化和浸润,这种作用可能与抑制白细胞与内皮细胞粘附分子的表达相关。     

甘草酸二铵对百草枯致急性肾损伤大鼠IL-17表达的影响

目的探讨甘草酸二铵(DG)对百草枯(PQ)中毒致急性肾损伤大鼠的保护作用及其可能机制。方法将50只SD大鼠按随机数字表法分为模型组(PQ组,n=20)、空白对照组(NS组,n=10)和干预组(DG组,n=20),PQ组和DG组大鼠给予PQ 100mg/kg一次性灌胃,NS组大鼠则给予等量生理盐水灌胃。DG组大鼠灌胃后立即给予甘草酸二铵50mg/kg于腹腔注射,每24h重复给药1次,直至72h后处死大鼠。取大鼠腹主动脉血,评估肾功能;病理学观察大鼠肾组织形态学改变情况,ELISA检测血清和肾组织IL-17及IL-16的含量。结果 HE染色结果显示,NS组大鼠肾组织结构正常;PQ染毒组大鼠可见肾小管管腔狭窄,甚至管腔闭锁,间质充血,细胞核固缩,细胞结构消失,肾小球结构紊乱;DG干预组大鼠肾组织病理改变较PQ染毒组大鼠明显减轻。肾功能结果显示,DG组大鼠血清Cr、BUN的水平明显低于PQ组(P0.01),但显著高于NS组(P0.01)。Elisa结果显示,DG组大鼠血清和肾组织中IL-6和IL-17的含量明显低于PQ组(P0.05),但显著高于NS组(P0.05)。结论甘草酸二铵可以减轻百草枯中毒大鼠的急性肾损伤,其机制可能与降低血清和肾组织中IL-6和IL-17的表达水平相关。     

甘草酸二铵对百草枯中毒致急性肺损伤大鼠TLR-4表达的影响

目的探讨甘草酸二铵(DG)对百草枯(PQ)中毒致急性肺损伤(ALI)大鼠的保护作用及其机制。方法选择健康SD大鼠50只,随机分为百草枯组(PQ组)、甘草酸二铵组(DG组)和正常对照组(NS组),PQ组和DG组予百草枯100mg/kg灌胃1次,DG组于灌胃后立即腹腔注射DG 50mg/kg,每日1次,对照组与PQ组注射等剂量的生理盐水。观察至48h处死大鼠,取肺组织检测肺湿干重比;肺组织HE染色评价肺组织损伤情况;采用RT-PCR法检测肺组织TLR-4mRNA和NF-κB mRNA的表达情况。另选择健康SD大鼠50只,分组及各组处置方法同上,观察其7天内死亡率。结果 PQ组与DG组肺湿干比、肺组织TLR-4mRNA和NF-κB mRNA表达较NS组明显升高(P0.01);DG组各指标明显低于PQ组(P0.01)。HE染色结果,NS组肺部结构正常,PQ组、DG组可见肺组织水肿、出血及炎性细胞浸润等肺损伤表现,DG组病变轻于PQ组。群体死亡率比较,PQ组7天死亡率为90%,DG组为40%,NS组无死亡。结论甘草酸二铵可减轻百草枯中毒致急性肺损伤大鼠肺部炎症,其机制可能与降低TLR-4、NF-κB的表达有关。     

The kinase activity of PKR represses inflammasome activity

The protein kinase R (PKR) functions in the antiviral response by controlling protein translation and inflammatory cell signaling pathways. We generated a transgenic, knock-in mouse in which the endogenous PKR is expressed with a point mutation that ablates its kinase activity. This novel animal allows us to probe the kinase-dependent and -independent functions of PKR. We used this animal together with a previously generated transgenic mouse that is ablated for PKR expression to determine the role of PKR in regulating the activity of the cryopyrin inflammasome. Our data demonstrate that, in contradiction to earlier reports, PKR represses cryopyrin inflammasome activity. We demonstrate that this control is mediated through the established function of PKR to inhibit protein translation of constituents of the inflammasome to prevent initial priming during innate immune signaling. These findings identify an important role for PKR to dampen inflammation during the innate immune response and caution against the previously proposed therapeutic strategy to inhibit PKR to treat inflammation.