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991.
Background
Methylobacterium extorquens AM1 is an aerobic facultative methylotrophic α-proteobacterium that can use reduced one-carbon compounds such as methanol, but also multi-carbon substrates like acetate (C2) or succinate (C4) as sole carbon and energy source. The organism has gained interest as future biotechnological production platform based on methanol as feedstock.Methodology/Principal Findings
We present a comprehensive study of all postulated enzymes for the assimilation of methanol and their regulation in response to the carbon source. Formaldehyde, which is derived from methanol oxidation, is assimilated via the serine cycle, which starts with glyoxylate and forms acetyl-CoA. Acetyl-CoA is assimilated via the proposed ethylmalonyl-CoA pathway, which thereby regenerates glyoxylate. To further the understanding of the central carbon metabolism we identified and quantified all enzymes of the pathways involved in methanol assimilation. We observed a strict differential regulation of their activity level depending on whether C1, C2 or C4 compounds are used. The enzymes, which are specifically required for the utilization of the individual substrates, were several-fold up-regulated and those not required were down-regulated. The enzymes of the ethylmalonyl-CoA pathway showed specific activities, which were higher than the calculated minimal values that can account for the observed growth rate. Yet, some enzymes of the serine cycle, notably its first and last enzymes serine hydroxymethyl transferase and malate thiokinase, exhibit much lower values and probably are rate limiting during methylotrophic growth. We identified the natural C1 carrying coenzyme as tetrahydropteroyl-tetraglutamate rather than tetrahydrofolate.Conclusion/Significance
This study provides the first complete picture of the enzymes required for methanol assimilation, the regulation of their activity levels in response to the growth substrate, and the identification of potential growth limiting steps. 相似文献992.
Simeon F. Kouam Yves L.N. Njonkou Guy Merlin Kuigoua Bonaventure T. Ngadjui Hidayat Hussain Ivan R. Green Barbara Schulz Karsten Krohn 《Phytochemistry letters》2010,3(4):185-189
Two prenylated anthranoids, psorantin and kenganthranol E, were isolated from the fruit of Psorospermum aurantiacum together with the known compounds ferruginin B, vismin, vismion D, haronginanthrone, kenganthranol B, kenganthraquinone, 1,7-dihydroxyxanthone, paradisiol, fridelin, fridelinol and betulinic acid. Their structures were determined on the basis of spectral data and by comparison with data reported in the literature as well as with authentic specimens for the known compounds. The structures of the new compounds were determined as bis-[3,8,9-trihydroxy-6-methyl-4,4-bis-(3,3-dimethylallyl)anthracenyl]methane (1) and 1,8,10-trihydroxy-6-methyl-4,5-bis-(3,3-dimethylallyl)-2,3-(2,2-dimethylpyrano)anthrone (2). Psorantin (1) is a dimer of vismin formed through a methylene linkage. The two new compounds when tested against the microbial strains Bacillus megaterium, Escherichia coli, Chlorella fusca and Microbotryum violaceum showed no activity. 相似文献
993.
Miguel Curto Luis Valledor Clara Navarrete Dolores Gutiérrez Hana Sychrova José Ramos Jesús Jorrin 《Journal of Proteomics》2010,73(12):2316-2335
By using a 2-DE based workflow, the proteome of wild and potassium transport mutant trk1,2 under optimal growth potassium concentration (50 mM) has been analyzed. At the exponential and stationary phases, both strains showed similar growth, morphology potassium content, and Vmax of rubidium transport, the only difference found being the Km values for this potassium analogue transport, higher for the mutant (20 mM) than for the wild (3–6 mM) cells.Proteins were buffer-extracted, precipitated, solubilized, quantified, and subjected to 2-DE analysis in the 5–8 pH range. More differences in protein content (37–64 mg g? 1 cell dry weight) and number of resolved spots (178–307) were found between growth phases than between strains. In all, 164 spots showed no differences between samples and a total of 105 were considered to be differential after ANOVA test. 171 proteins, corresponding to 71 unique gene products have been identified, this set being dominated by cytosolic species and glycolitic enzymes. The ranking of the more abundant spots revealed no differences between samples and indicated fermentative metabolism, and active cell wall biosynthesis, redox homeostasis, biosynthesis of amino acids, coenzymes, nucleotides, and RNA, and protein turnover, apart from cell division and growth. PCA analysis allowed the separation of growth phases (PC1 and 2) and strains at the stationary phase (PC3 and 4), but not at the exponential one. These results are also supported by clustering analysis. As a general tendency, a number of spots newly appeared at the stationary phase in wild type, and to a lesser extent, in the mutant. These up-accumulated spots corresponded to glycolitic enzymes, indicating a more active glucose catabolism, accompanied by an accumulation of methylglyoxal detoxification, and redox-homeostasis enzymes. Also, more extensive proteolysis was observed at the stationary phase with this resulting in an accumulation of low Mr protein species. 相似文献
994.
Shaheen Asghar Andres Magnusson Azad Khan Keramat Ali Akhtar Hussain 《Obesity (Silver Spring, Md.)》2010,18(6):1143-1145
The aim of this study was to examine whether the association between overweight and depression usually found in western societies would also be found in locations where overweight is not stigmatized. A total of 1,271 individuals from rural Bangladesh were randomly selected; the response rate was 76%. Depressive symptoms were measured with the Montgomery‐Åsberg Depression Rating Scale (MADRS). The sum MADRS scores were 13.4 (s.d. = 5.8) and 18.5 (8.1) for overweight vs. nonoverweight (t = 6.6; P < 0.000) men, respectively, and 19.7 (7.8) and 23.2 (7.9) for overweight vs. nonoverweight women, respectively (t = 4.2; P < 0.000). Thus the MADRS score was lower in overweight individuals. After adjusting for sex and age, BMI significantly predicted the MADRS score (β = ?0.3; t = 10.2; P < 0.000). These findings suggest that overweight may be related to fewer depressive symptoms in non western cultures. 相似文献
995.
Iman M. Ahmad Ebtihal H. Mustafa Noor H. Mustafa Lubna H. Tahtamouni Maher Y. Abdalla 《Central European Journal of Biology》2010,5(6):739-748
2DG causes cytotoxicity in cancer cells by disrupting thiol metabolism while Doxorubicin (DOX) induces cytotoxicity in tumor
cells by generating reactive oxygen species (ROS). Here we examined the combined cytotoxic action of 2DG and DOX in rapidly
dividing T47D breast cancer cells vs. slowly growing MCF-7 breast cancer cells. T47D cells exposed to the combination of 2DG/DOX
significantly decreased cell survival compared to controls, while 2DG/DOX had no effect on MCF-7 cells. 2DG/DOX also disrupted
the oxidant status of T47D treated cells, decreased intracellular total glutathione and increased glutathione disulfide (%GSSG)
compared to MCF-7 cells. Lipid peroxidation increased in T47D cells treated with 2DG and/or DOX, but not in MCF-7 cells. T47D
cells were significantly protected by NAC, indicating that the combined treatment exerts its action by increasing ROS production
and disrupting antioxidant stores. When we inhibited glutathione synthesis with BSO, T47D cells became more sensitive to 2DG/DOX-induced
cytotoxicity, but NAC significantly reversed this cytotoxic effect. Finally, 2DG/DOX, and BSO significantly increased the
%GSSG in T47D cells, an effect which was also reversed by NAC. Our results suggest that exposure of rapidly dividing breast
cancer cells to 2DG/DOX enhances cytotoxicity via oxidative stress and via disruptions to thiol metabolism. 相似文献
996.
Butt RH Lee MW Pirshahid SA Backlund PS Wood S Coorssen JR 《Journal of proteome research》2006,5(11):3161-3172
Human preterm labor (PL) is the single most significant problem in modern Obstetrics and Gynecology, affecting approximately 10% of pregnancies worldwide, constituting the leading cause of perinatal mortality and morbidity, and contributing significantly to chronic childhood disease. Currently, our molecular understanding of PL remains staggeringly inadequate to reliably diagnose or rationally intervene in PL events; several molecular alterations have been implicated in PL, but these have proven of limited value as diagnostic/prognostic markers. The majority of PL events remain spontaneous and unpredictable: critical care emergencies. Here, we apply functional proteomics to dissect molecular mechanisms of human PL. Human placental tissue was collected in clearly differentiated cases of preterm and term labor. Highly refined two-dimensional gel electrophoresis (2DE) was used for protein separation, coupled with automated differential gel image analysis to compare the resulting proteomic maps. For this initial study, only the most important protein differences were selected for further analysis, that is, proteins that were unique to one sample, and absent from the other, with 100% reproducibility across the sample population. In total, 11 such proteins were identified by tandem mass spectrometry, falling into three distinct functional classes: structural/cytoskeletal components, ER lumenal proteins with enzymatic or chaperone functions, and proteins with anticoagulant properties. These expression changes form the groundwork for further molecular investigation of this devastating medical condition. This approach therefore holds the potential not only to define the underlying molecular components, but also to identify novel diagnostic tools and targets for rational drug intervention. 相似文献
997.
Christoph Reisinger Friso van Assema Martin Schürmann Zahid Hussain Peter Remler Helmut Schwab 《Journal of Molecular Catalysis .B, Enzymatic》2006,39(1-4):149-155
Direct visualization of the activity of enzymes expressed by bacterial colonies attached to a solid support, often referred to as “filter assay”, is a powerful strategy for the identification of new or improved biocatalysts. In this work we demonstrate the usefulness of NAD+/NADH coupled enzymatic reactions as visualization tool in such experimental setups. Dehydrogenases, capable of oxidizing or reducing the reaction product released from the bacterial colony were supplemented to the screening solution, together with the screening substrate and a sufficient amount of NAD+ or NADH, respectively. We also examined the screening of directly NAD+/NADH coupled reactions. The release or consumption of NADH in the area of colonies was monitored on behalf of its fluorescence at 450 nm. Excitation was achieved by standard “black-light” UV tubes (340–360 nm). The visible fluorescence signal was recorded using a CCD-camera. We got excellent results for the screening of threonine aldolases and esterases and were able to show the principle utility for amidase, nitrilase, nitrile hydratase, hydroxynitrile lyase and benzaldehyde dehydrogenase active colonies. 相似文献
998.
Khan WN Lodhi MA Ali I Azhar-Ul-Haq Malik A Bilal S Gul R Choudhary MI 《Journal of enzyme inhibition and medicinal chemistry》2006,21(1):17-19
Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of Ranunculus repens led to the isolation of methyl 3,4,5-trihydroxybenzoate 1, R(+)- 4-methoxydalbergione 2 and R(+)-dalbergiophenol 3. The structures of these compounds were established through spectral studies including 1D and 2D NMR experiments and by comparison with literature data. These compounds showed potent inhibitory activity against urease. 相似文献
999.
Using DNA and RNA heptanucleotides containing an unnatural L-nucleotides as well as the complementary strands, effects of the introduction of an L-nucleotide on the structure of DNA/DNA, RNA/RNA, and DNA/RNA duplexes were investigated by circular dichroism experiments and RNase H-mediated RNA strand cleavage reaction. The results suggested that the substitution of the central D-nucleotide with an L-nucleotide in the duplexes causes the significant structural alterations as the duplex structures change to conformations with more B-form similarities. 相似文献
1000.
Zidan AS Sammour OA Hammad MA Megrab NA Hussain MD Khan MA Habib MJ 《AAPS PharmSciTech》2006,7(3):E38-E46
The purpose of this study was to develop poly(d,1-lactic-coglycolic acid) (PLGA)-based anastrozole microparticles for treatment
of breast cancer. An emulsion/extraction method was used to prepare anastrozole sustained-release PLGA-based biodegradable
microspheres. Gas chromatography with mass spectroscopy detection was used for the quantitation of the drug throughout the
studies. Microparticles were formulated and characterized in terms of encapsulation efficiency, particle size distribution,
surface morphology, and drug release profile. Preparative variables such as concentrations of stabilizer, drug-polymer ratio
polymer viscosity, stirring rate, and ratio of internal to external phases were found to be important factors for the preparation
of anastrozole-loaded PLGA microparticles. Fourier transform infrared with attenuated total reflectance (FTIR-ATR) analysis
and differential scanning calorimetry (DSC) were employed to determine any interactions between drug and polymer. An attempt
was made to fit the data to various dissolution kinetics models for multiparticulate systems, including the zero order, first
order, square root of time kinetics, and biphasic models. The FTIR-ATR studies revealed no chemical interaction between the
drug and the polymer. DSC results indicated that the anastrozole trapped in the microspheres existed in an amorphous or disordered-crystalline
status in the polymer matrix. The highest correlation coefficients were obtained for the Higuchi model, suggesting a diffusion
mechanism for the drug release. The results demonstrated that anastrozole microparticles with PLGA could be an alternative
delivery method for the long-term treatment of breast cancer.
Published: July 21, 2006 相似文献