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1.
BACKGROUND: Amino acid dehydrogenases (L-amino acid: oxidoreductase deaminating; EC 1.4.1.X) are members of the wider superfamily of oxidoreductases that catalyze the reversible oxidative deamination of an amino acid to its keto acid and ammonia with the concomitant reduction of either NAD+, NADP+ or FAD. These enzymes have been received much attention as biocatalysts for use in biosensors or diagnostic kits to screen amino acid metabolism disorders such as phenylketonuria (PKU), maple syrup urine disease (MSUD), homocystinuria (HCY) and hyperprolinemia. This study was aimed to isolation and screening of novel amino acid dehydrogenases from soil bacteria. METHODS: The enzyme producing bacteria were selected among L-methionine and L-phenylalanine utilizers isolated from soil by thin layer chromatography, activity staining and confirmed by enzyme assay. Bacterial strains were identified by phenotypic and biochemical characteristics. The steady-state kinetic studies of enzymes were also performed. RESULTS: In total of 230 tested strains, four of them were recognized as amino acid dehydrogenase producers that belong to species of Pseudomonas, Citrobacter and Proteus. They exhibited the desired NAD+-dependent dehydrogenase activities toward L-isoleucine, L-methionine, L-cysteine, L-serine and L-glutamine in oxidative deamination reaction. The specific activity of L-isoleucine dehydrogenase, L-methionine dehydrogenase and L-glutamine dehydrogenase for oxidative deamination of L-isoleucine, L-methionine and L-glutamine were 1.59, 1.2 and 0.73 U/mg, respectively. The Kcat/Km (s(-1).mM(-1)) values in these strains were as follows: L-isoleucine, 113.6, L-methionine, 62.05 and L-glutamine, 95.83. CONCLUSION: This is the first report of occurrence a specific isoleucine dehydrogenase, glutamine dehydrogenase and methionine dehydrogenase in bacteria.  相似文献   

2.
基于GGE-biplot的大豆根瘤菌抗逆性资源筛选   总被引:2,自引:0,他引:2  
为了准确评价大豆根瘤菌在干旱及酸碱环境中的稳定性和适应性,采用GGE双标图对黑龙江省不同生态区分离、鉴定、纯化的7个大豆根瘤菌菌株分别进行耐旱性、耐酸碱性能力分析评价。结果表明:各供试菌株随着PEG6000浓度的增加,菌株生长量均呈现逐渐下降的趋势。GGE双标图分析表明,耐旱性强且稳定性较好的菌株为111-1;供试菌株在耐酸碱性上均有较大优势,菌株在pH3.0和pH12.0的环境条件下均能缓慢生长,并且均在pH9.0的环境条件下生长量最大。GGE双标图分析得出,耐酸性强且稳定性较好的菌株为112-2,耐碱性强且稳定性较好的菌株为111-3。该结果对适于黑龙江地区不同环境条件下大豆根瘤菌的应用具有重要的指导意义。  相似文献   

3.
Dothideaceous black yeast-like fungi (BYF) are known to synthesise DHN-melanin that is inhibited by the systemic fungicide tricyclazole. The final step of the DHN melanin pathway is the conjoining of 1,8-DHN molecules to form the melanin polymer. There are several candidate enzymes for this step, including phenoloxidases such as tyrosinase and laccases, peroxidases, and perhaps also catalases. We analysed the type polyphenoloxidases that are involved in biosynthesis of BYF melanins. For that purpose we used substrates of o-diphenoloxidases (EC 1.10.3.1.): 4-hydroxyphenyl-pyruvic acid, L-β-phenyllactic acid, tyrosine, pyrocatechol, 3,4-dihydroxyphenylalanine and homogentisic acid, as well as substrates of p-diphenoloxidases (EC 1.10.3.2.): syringaldazine, resorcinol, p-phenylenediamine, phloroglucinol, guaiacol and pyrogallic acid. Fourteen strains of black yeasts originating from different natural biotopes were investigated. The tested strains could be divided into four groups based on their ability to produce dark pigments when cultivated on aromatic substrates of o- and on p-diphenoloxidases. It was established that syringaldazine, pyrogallic acid and 4-hydrophenyl-pyruvic acid, β-phenyllactic acid optimally promote melanin biosynthesis. Average intensity of pigmentation of all strains studied was minimal when guaiacol was used as a substrate. The present investigation indicates that the melanisation process may involve more enzymes and more substrates than those commonly recognised. Black yeasts are likely to contain a multipotent polyphenoloxidase.  相似文献   

4.
盐碱胁迫伴随作物生长各个阶段,筛选获得全生育期耐盐碱大豆资源意义重大。试验通过测定大庆地区盐碱土含盐碱种类、含盐量及pH值等指标,确定筛选用盐碱种类、浓度。在培养皿、发芽袋和盆栽试验筛选中,通过大豆芽期发芽率、芽苗期物质生长量、成熟期物质生长量鉴定耐盐碱大豆种质。结果显示大庆地区盐碱土壤为硫酸盐苏打盐碱土,确定盐碱溶液为NaCl、Na2CO3、NaHCO3和Na2SO4(摩尔比为1∶1∶9∶9)的混合盐碱溶液,以Na离子含量计算总盐浓度为80 mmol·L-1,溶液pH值为8.9,盆栽筛选用土壤盐含量为3.3‰,pH值为8.9。鉴定的887份种质资源中种皮颜色有黑、褐、红、绿、黄及双色等,相关性分析发现大豆耐盐碱性与大豆种皮颜色极显著正相关。通过芽期耐盐碱鉴定,887份大豆资源中筛选获得296份耐以上资源,进一步芽苗期筛选有123份显示高耐,再经过全生育期筛选获得7份高耐资源,5份来源于南方,2份来源于黄淮,62份耐资源,盆栽筛选比例为56.10%。本研究建立了从芽期、芽苗期到全生育期的逐级筛选方法,从887份大豆种质资源中筛选获得69份耐盐碱资源,为耐盐碱育种与耐盐碱基因资源利用提供基础材料。  相似文献   

5.
Summary Tubers of clones from a diploid hybrid population ofSolanum phureja andS. stenotomum were screened for resistance to tuber soft rot caused by strains ofErwinia carotovora subsp.atroseptica (Eca),E. carotovora subsp.carotovora (Ecc) andE. chrysanthemi (Ech). Significant, positive correlations between resistance to the different strains and species were observed, indicating that screening for resistance to tuber soft rot could be accomplished by using just one of the three pathogens. Strains of Ecc and Ech were found to be much more virulent than strains of Eca. Inoculating with Ecc and Ech resulted in more distinct differences among susceptible, moderately resistant and resistant clones than inoculating with Eca.  相似文献   

6.
Background: Phenylalanine dehydrogenase (PheDH; EC 1.4.1.20) is a NAD+-dependent enzyme that performs the reversible oxidative deamination of L-phenylalanine to phenylpyruvate. It plays an important role in detection and screening of phenylketonuria (PKU) diseases and production of chiral intermediates as well. The main goal of this study was to find a simple and rapid alternative method for purifying PheDH. Methods: The purification of recombinant Bacillus sphaericus PheDH was investigated in polyethylene glycol (PEG) and ammonium sulfate aqueous two-phase systems (ATPS). The influences of system parameters including PEG molecular weight and concentration, pH and (NH4)2SO4 concentration on enzyme partitioning were also studied. The purity of enzyme was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Results: A single extraction process was developed for separation and purification of recombinant PheDH from E. coli BL21 (DE3). The optimized conditions for partitioning and purification of PheDH were 9% (w/w) PEG-6,000 and 16% (w/w) (NH4)2SO4 at pH 8.0. The partition coefficient, recovery, yield, purification factor and specific activity values were achieved 58.7, 135%, 94.42%, 491.93 and 9828.88 U/mg, respectively. Also, the Km values for L-phenylalanine and NAD+ in oxidative deamination were 0.21 and 0.13 mM, respectively. Conclusion: The data presented in this paper demonstrated the potential of ATPS as a versatile and scaleable process for downstream processing of recombinant PheDH.  相似文献   

7.
Soil salinity and alkalinity adversely affects the productivity and grain quality of rice.The grain quality of 19 rice genotypes characterized as salt tolerant (T),semi-tolerant (ST) and sensitive (S) was assessed in lysimeters containing saline and highly alkaline soils.Head rice recovery was reduced by salinity stress whereas it was not affected by alkalinity stress.The ratio of length to width (grain dimensions) was significantly reduced in the T genotype even at low electrical conductivity (EC,4 mS/cm) and alkalinity (pH 9.5),whereas in the ST genotype,it was significantly reduced at high salinity (EC 8 mS/cm).There was no significant effect of any levels of salinity or alkalinity on grain dimensions in the S genotype.Amylose content was significantly reduced in T and ST groups even at low EC (4 mS/cm) and alkalinity (pH 9.5) and the effect in the S genotype was only at high salinity.Starch content showed significant reduction at high salinity and alkalinity (EC 8 mS/cm and pH 9.8) in the T and ST genotypes and no significant effect was observed in the S genotype.The effect of both levels of salinity (EC 4 and 8 mS/cm) and high alkalinity (pH 9.8) on gel consistency was observed only in the S genotype.The tolerant genotypes IR36 under high salinity,and CSR10 and CSR11 under alkali stress showed less reduction in amylose content.The T genotype BR4-10,and ST genotypes CSR30,CSR29 and CSR13 showed better gel consistency under saline and alkali stress.Amylose content was affected even at low salinity stress and thus important to be considered in breeding rice for salt tolerance.Overall,the grain quality of T and ST genotypes was less affected by saline and alkali stress compared to S ones.  相似文献   

8.
为比较几种固定条件对不同植物材料样品电镜超微结构图像清晰度的影响。以3个不同科属4种植物[油棕(Elaeis gineansis Jacq.)、拟南芥(Arabidopsis thaliana.)、花生(Arachis hypogaea Linn.)、柱花草(Stylosanthes guianensias Sw.)]为研究主体代表,探讨了2.5%戊二醛与4%戊二醛固定过夜、锇酸固定2 h及过夜的制备方法对其叶片超微结构的影响,并成功观察了柱花草接种胶苞炭疽野生型菌株CH008后的病菌侵入过程。结果表明:油棕、拟南芥、花生及柱花草叶片经4%戊二醛与1%锇酸固定液固定过夜,其组织成像的效果均较为理想,各种细胞器整体信息丰富、结构组织完好、线条清晰。表明,此制备方法能够较好的保存植物叶片和细胞组织,提高制样的成功率及观察分辨率。  相似文献   

9.
从生物学、致病力、对甲霜灵的敏感性等侧面对海南岛19个县市的芋疫霉菌(Phy-tophthora colocasiae Racib)进行研究,结果表明:芋疫霉种下存在丰富的多样性。孢襄形态差异显著,长宽比1.36~2.6,大小从(17.5-)39.5(-82.5)×(10.0-)23.3(-35.0)μm到(40.0-)56.0(-92.5)×(22.5-)30.5(-40.0)μm。大部分菌株的最适生长温度25~30℃,最适温度下各菌株的生长速率差异显著,从0.562cm/d到0.829cm/d。两种交配型(A1:A2)比例接近于1。各菌株对芋头材料的致病力有明显不同。对甲霜灵的敏感性也显著不同,EC50值0.077 μg/mL~0.448μg/mL。生物学、致病力、对甲霜灵的敏感性等性状的分布似乎与地理位置有关。多元聚类将19个菌株分成6类。  相似文献   

10.
为筛选防治橡胶树白粉病安全有效的植物源杀菌剂,采用孢子萌发抑制法测定22种植物甲醇提取液对橡胶树白粉病菌孢子的抑菌活性.结果表明,假臭草和九里香提取液浓度在0.1 g/mL时,对橡胶树白粉病菌孢子的萌发抑制率分别为43.98%和47.62%,极显著优于其它植物和对照.进一步测定假臭草和九里香提取液的EC50和EC75值,以及其盆栽试验的防治效果与橡胶树叶片丙二醛(MDA)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和苯丙氨酸解氨酶(PAL)的活性.结果表明,假臭草和九里香对病原菌孢子的EG50值分别为0.26 g/mL和0.20 g/mL,EC75值分别为1.12 g/mL和0.99 g/mL.假臭草和九里香提取液浓度在EC75值时,防病效果分别为20.00%和18.67%,显著高于对照.假臭草和九里香提取液处理后,橡胶树叶片的MDA含量极显著低于对照,CAT、SOD和PAL活性则显著或极显著高于对照.由此可见,假臭草和九里香提取液不仅能抑制病原菌的萌发和生长,而且能提高橡胶树的抗病性.  相似文献   

11.
Chalkiness is one of the key factors determining rice quality and price. Ascorbic acid(Asc) is a major plant antioxidant that performs many functions in plants. L-Galactono-1,4-lactone dehydrogenase(L-Gal LDH, EC1.3.2.3) is an enzyme that catalyzes the final step of Asc biosynthesis in plants. Here we show that the L-Gal LDH-overexpressing transgenic rice, GO-2,which has constitutively higher leaf Asc content than wild-type(WT) plants, exhibits significantly reduced grain chalkiness. Higher foliar ascorbate/dehydroascorbate(Asc/DHA)ratios at 40, 60, 80, and 100 days of plant age were observed in GO-2. Further investigation showed that the enhanced level of Asc resulted in a significantly higher ribulose-1,5-bisphosphate(Ru BP) carboxylase/oxygenase(Rubisco) protein level in GO-2 at 80 days. In addition, levels of abscisic acid(ABA) and jasmonic acid(JA) were lower in GO-2 at 60, 80, and100 days. The results we present here indicate that the enhanced level of Asc is likely responsible for changing redox homeostasis in key developmental stages associated with grain filling and alters grain chalkiness in the L-Gal LDH-overexpressing transgenic by maintaining photosynthetic function and affecting phytohormones associated with grain filling.  相似文献   

12.
A new designed dye sensor based on indole as a donor unit and benzothiazole as an acceptor unit have provided very clear optical switching functions when monitored with a pH triggered molecular chemosensor effects in the presence of alkali/acid addition. The prepared dye sensor shows cleared fluorescence quenching effect with alkali addition. The level of energy potential and the electron distribution of this compound were calculated by computational simulation approaches.  相似文献   

13.
Rubiaceae family is a large family of 630 genera and about 13000 species found worldwide, especially in tropical and warm regions. These plants are not only ornamental but they are also used in African folk medicine to treat several diseases. Based on online published data and library bibliographic research, we herein reported accumulated information related to their traditional usages in sub-Saharan traditional medicine, their chemical composition and the screened pharmacological activities. Indeed, more than 60 species are used for more than 70 medicinal indications including malaria, hepatitis, eczema, oedema, cough, hypertension, diabetes and sexual weakness. Through biological screening following leads supplied with traditional healers, many of these plants exhibited antimalarial, antimicrobial, antihypertension, antidiabetic, antioxidant and anti-inflammatory activities. Bioactive compounds including indole alkaloids, terpenoids and anthraquinones have been isolated from these bioguided fractionation studies. It is evidence that great attention has been paid to species such as Nauclea latifolia, Morinda lucida, Mitragyna inermis and Crossopteryx febrifuga; however, several compounds should be waiting to be discovered since none of these plants has been systematically investigated for its biochemical composition. According the current global health context with the recrudescence of HIV, much effort should be oriented towards this virus when screening Rubiaceae.  相似文献   

14.
用卤虫生物测试法对茯砖茶中分离的21株散囊菌进行产毒性筛选。在蔗糖酵母浸汁培养基上培养的散囊菌滤液用卤虫幼虫进行毒性测定,发现47.6%的菌株培养液对卤虫呈现毒性。其中毒性最大的是匍匐散囊菌032号,其培养液对卤虫的 LC_(60)是0.164μ1/m1,它的卤虫毒性单位是6098μ1/m1,并可引起小鼠急性中毒死亡。冠突散囊菌除1株菌外对卤虫幼虫不呈现毒性。文中还对散囊菌的培养性质、产毒特点作了分析和讨论。认为茯砖茶中除冠突散囊菌之外,其它散囊菌不应存正。  相似文献   

15.
Previously, we showed that Ecklonia cava polyphenol (ECP) treatment suppressed ethanol-induced increases in hepatocyte death by scavenging intracellular reactive oxygen species (ROS) and maintaining intracellular glutathione levels. Here, we examined the effects of ECP on the activities of alcohol-metabolizing enzymes and their regulating mechanisms in ethanol-treated hepatocytes. Isolated hepatocytes were incubated with or without 100 mM ethanol. ECP was dissolved in dimethylsulfoxide. ECP was added to cultured cells that had been incubated with or without ethanol. The cells were incubated for 0–24 h. In cultured hepatocytes, the ECP treatment with ethanol inhibited cytochrome P450 2E1 (CYP2E1) expression and activity, which is related to the production of ROS when large quantities of ethanol are oxidized. On the other hand, ECP treatment with ethanol increased the activity of alcohol dehydrogenase (ADH) and aldehyde dehydrogenase. These changes in activities of CYP2E1 and ADH were suppressed by treatment with H89, an inhibitor of protein kinase A. ECP treatment with ethanol enhanced cyclic AMP concentrations compared with those of control cells. ECP may be a candidate for preventing ethanol-induced liver injury via regulating alcohol metabolic enzymes in a cyclic AMP-dependent manner.  相似文献   

16.
茶皂素对雷公藤乳油防治茶尺蠖幼虫的增效作用   总被引:2,自引:0,他引:2  
测定了茶皂素对雷公藤乳油防治茶尺蠖幼虫的增效作用。结果表明,用1、2、4mg/ml茶皂素浸叶处理,对茶尺蠖2龄幼虫的毒杀作用不明显,第7天的毒杀效果只有27.03%~37.84%。用雷公藤乳油0.8、1.6、3.2、6.4mg/ml和12.8mg/ml浸叶处理,对茶尺蠖2龄幼虫的毒杀效果在第7天分别为27.27%、33.78%、40.54%、56.76%和63.51%。在0.8mg/ml浓度的雷公藤乳油中加入4mg/ml的茶皂素,对茶尺蠖幼虫的毒杀作用(84.42%)显著高于加1mg/ml茶皂素的毒杀效果(68.83%);而加入2mg/ml和4mg/ml的防效差异不显著。向不同浓度的雷公藤乳油中加入2mg/ml茶皂素,对茶尺蠖2龄幼虫的共毒系数在第1、3、5、7天分别为667.68、981.61、1706.15和1209.76,即增效5.68~11.10倍,达到相同的使用效果可减少雷公藤用量85%以上。对茶尺蠖4龄幼虫增效1.00~6.91倍,减少雷公藤用量50%以上。  相似文献   

17.
A major alginate lyase, FlAlyA, was purified from the periplasmic fraction of an alginate-assimilating bacterium, Flavobacterium sp. strain UMI-01. FlAlyA showed a single band of ~30 kDa on SDS-PAGE and exhibited the optimal temperature and pH at 55 °C and pH 7.7, respectively. Analyses for substrate preference and reaction products indicated that FlAlyA was an endolytic poly(mannuronate) lyase (EC 4.2.2.3). A gene fragment encoding the amino-acid sequence of 288 residues for FlAlyA was amplified by inverse PCR. The N-terminal region of 21 residues except for the initiation Met in the deduced sequence was predicted as the signal peptide and the following region of six residues was regarded as propeptide, while the C-terminal region of 260 residues was regarded as the polysaccharide-lyase-family-7-type catalytic domain. The entire coding region for FlAlyA was subjected to the pCold I—Escherichia coli BL21(DE3) expression system and ~eight times higher yield of recombinant FlAlyA (recFlAlyA) than that of native FlAlyA was achieved. The recFlAlyA recovered in the periplasmic fraction of E. coli had lost the signal peptide region along with the N-terminal 3 residues of propeptide region. This suggested that the signal peptide of FlAlyA could function in part in E. coli.  相似文献   

18.
杨德  盖钧镒 《大豆科学》1993,12(1):23-29
采用南方3769份夏大豆地方品种按省分层随机抽样所得143份材料在南京两年三重复试验结果,按三个优蛋白(胱氨酸组分、甲硫氨酸组分、含硫氨基酸组分)性状值高低,剖分出相应的三个蛋白特异群体及地方群体。判别分析得到,高胱氨酸、高甲硫氨酸、高含硫氨基酸等三个特异群体由农艺性状构成的19个简易判别函数中,有17个与经济系数或粒茎比有关。三个优蛋白性状与经济系数或高粒茎比密切相关。选择高经济系数或高粒茎比后,胱氨酸组分及含硫氨基酸组分间接地显著相对提高5~7%,甲硫氨酸组分略有增加。由此建议高经济系数或高粒茎比,可作为优蛋白资源的田间筛选指标。在资源评价中可考虑经济系数或粒茎比作为鉴定指标之一。  相似文献   

19.
The digestion and Volatile Fatty Acid (VFA) production from rice straw and oil palm fronds by cellulolytic bacteria isolated from the termite Coptotermes curvignathus were investigated. The bacteria were Acinetobacter strain Raminalimon, Enterobacter aerogenes strain Razmin C, Enterobacter cloacae strain Razmin B, Bacillus cereus strain Razmin A and Chryseobacterium kwangyangense strain Cb. Acinetobacter strain Raminalimon is an aerobic bacterium, while the other species are facultative anaerobes. There were significant differences (p<0.05) among the bacteria for Dry Matter (DM) lost and acetic acid production from rice straw and Acinetobacter strain Raminalimon showed the highest activity. The facultative bacteria C. kwangyangense strain Cb (cfu mL(-1) 231 x 10(-6), OD: 0.5), E. cloacae (cfu mL(-1) 68 x 10(-7), OD: 0.5) and E. aerogenes (cfu mL(-1) 33 x 10(-7), OD: 0.5) were used for digestion study with the rumen fluid microflora. The in vitro gas production technique was applied for the comparative study and the parameters measured were pH, gas (volume), dry matter lost, acetic acid, propionic acid and butyric acid concentrations. pH was not significantly (p<0.05) different among the five treatments. The bacterium C. kwangyangense strain Cb showed the highest activity (p<0.05) for DM lost, acetic acid, propionic acid and butyric acid production from rice straw when compared to the other bacterial activities. There was no significance (p<0.05) difference between the three bacteria for the dry matter lost of oil palm fronds but the production of Volatile Fatty Acids (VFA) was significantly (p<0.05) high in the treatment which was inoculated with C. kwangyangense strain Cb. The Gen Bank NCBI/EMBL accession numbers for the bacterial strains are EU332791, EU305608, EU305609, EU294508 and EU169201.  相似文献   

20.
Background: During the last decade, enterococci have become important nosocomial pathogens, representing the second leading cause of urinary tract infections. This increasing prevalence has been paralleled by the occurrence of multi-drug resistant (MDR) and high-level gentamicin resistant (HLGR) strains. Methods: From September 2005 to 2006, a total of 638 enterococcal isolates were collected from urine samples among 9 medical centers in Tehran (Iran). Confirmation of species and detection of gentamicin resistance genes were done by PCR method. Anti-microbial susceptibility test was determined with disk diffusion and minimal inhibitory concentration of gentamicin among HLGR isolates assayed by microdilution methods. Results: The isolates were found to consist of Enterococcus faecalis (77.8%) and Enterococcus faecium (22.2%). The results obtained from PCR showed a high rate of agreement with phenotypic assays for both species. MDR to most prevalent anti-microbials was present in 29% and 72% of the E. faecalis and E. faecium isolates, respectively. HLGR phenotype was detected in 64% of E. faecalis and 92% of E. faecium isolates. The aac(6')-Ie-aph(2')-Ia gene were identified in 83% of E. faecalis and 100% of E. faecium HLGR isolates. E. faecalis and E. faecium isolates differed in their susceptibilities to different antibiotics. Conclusion: Emergence of multi-resistant enterococci and high level resistance to gentamicin shown by enterococcal strains is of concern because of the decrease in the therapeutic options for treatment of infections caused by enterococci.  相似文献   

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