Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.2.1.1 (ACS)
 78,556 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The acetate activating system of Acetobacter aceti has been studied. The enzyme responsible, acetyl-CoA synthetase, has been purified about 500-fold from crude cell extracts and was approximately 85% pure as judged by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. The purified enzyme showed optimal activity at pH 7.6 in both Tris-HCL and potassium phosphate buffers. In its purest form, the enzyme was stable at 4 degrees-C but denatured upon freezing. The Km values for CoA, ATP and acetate were found to be 0.104 mM, 0.36 mM and 0.25 mM respectively; propionate and acrylate were also activated by the enzyme but not butyrate, isobutyrate or valerate. GTP, UTP, CTP and ADP could not replace ATP in the reaction, and cysteine or pantetheine failed to replace CoA. The cationic requirements were studied and of the divalent cations tested, only Mn2+ could significantly replace Mg2+ in the reaction; K+ and NH4+ stimulated enzyme activity but inhibited at high concentrations; Na+ was a poor activator, but did not inhibit at higher concentrations. The effect of a number of glucose and other metabolites on enzyme activity has been tested.
 ...
PMID:Characterization of the acetyl-CoA synthetase of Acetobacter aceti. 1

1. Acetate-CoA ligase, acetyl-CoA-carbon dioxide ligase and fatty acid synthetase were shown to be present in particle-free fractions of guinea-pig intestinal mucosa. 2. Each of these enzymes was partially purified by ammonium sulphate precipitation from the particle-free supernatant. 3. The incorporation of acetate and citrate into fatty acid was measured. 4. Gas-liquid radiochromatography was used to investigate the pattern of fatty acids synthesized. 5. The rate-limiting step in fatty acid synthesis was shown to be acetyl-CoA-carbon dioxide ligase.
 ...
PMID:Fatty acid synthesis in intestinal mucosa of guinea pig. 438 98

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.
 ...
PMID:The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm. 439 82

1. The lipogenic enzyme ATP citrate lyase (ATP:citrate oxaloacetate-lyase (pro-3S-CH2COO-acetyl-CoA; ATP-dephosphorylating), EC 4.1.3.8) is partially purified from human liver by ammonium sulfate fractionation and anionexchange chromatography. 2. Km values for the substrates are 1.1 x 10(-5) 1.3 x 10(-3), and 1.2 x 10(-4) M for CoASH, ATP and citrate, respectively. The hypolipidemic drug L(-)-hydroxycitrate is a competitive inhibitor with respect to citrate (Ki = 3 x 10(-4) M). 3. Specific activities measured in liver, adipose tissue and intestinal mucosa (autopsic and biopsic material) are in the range of 1 mU/mg protein suggesting that the citrate pathway does not significantly contribute to human lipogenesis. No stimulation is found after a 3-day carbohydrate-rich diet. 4. Specific activities of other key-enzymes of the acetyl-CoA production from carbohydrates (pyruvate dehydrogenase, cytosolic acetyl-CoA synthetase) are of the same low magnitude.
 ...
PMID:Properties and organ distribution of ATP citrate (pro-3S)-lyase. 741 78

Separation of the ammonium sulfate precipitated protein fraction of mouse ascitic fluid, containing the specific immunoglobulin (pI 6.7-6.8; molecular weight 180000), from ammonium sulfate was investigated by means of non-traditional dialysis, based on the difference in diffusion rates of small and large molecules through porous membranes. The experiments were carried out in spiral membrane modules equipped with a Neosepta (AM-2 or ACS-SB) anion exchange membrane and a microfiltration membrane (Synpore or Sartorius). To enhance the driving force for penetration of ammonium sulfate and low-molecular-weight components from solution of ascitic protein fraction into water, a counterpressure was imposed on the side of microfiltration membrane. The flow rate, counterpressure and the pore sizes of microfiltration membranes had a significant effect on the separation process, as expected. The type of the anion exchange membrane had only a small effect. This process makes it possible to desalt the immunoglobulin fraction with high purity and yield in a few hours instead of 5 days.
 ...
PMID:Separation of specific immunoglobulin. 1. Desalination using a membrane system. 776 50

Fungal ammonia fermentation is a novel dissimilatory metabolic mechanism that supplies energy under anoxic conditions. The fungus Fusarium oxysporum reduces nitrate to ammonium and simultaneously oxidizes ethanol to acetate to generate ATP (Zhou, Z., Takaya, N., Nakamura, A., Yamaguchi, M., Takeo, K., and Shoun, H. (2002) J. Biol. Chem. 277, 1892-1896). We identified the Aspergillus nidulans genes involved in ammonia fermentation by analyzing fungal mutants. The results showed that assimilatory nitrate and nitrite reductases (the gene products of niaD and niiA) were essential for reducing nitrate and for anaerobic cell growth during ammonia fermentation. We also found that ethanol oxidation is coupled with nitrate reduction and catalyzed by alcohol dehydrogenase, coenzyme A (CoA)-acylating aldehyde dehydrogenase, and acetyl-CoA synthetase (Acs). This is similar to the mechanism suggested in F. oxysporum except A. nidulans uses Acs to produce ATP instead of the ADP-dependent acetate kinase of F. oxysporum. The production of Acs requires a functional facA gene that encodes Acs and that is involved in ethanol assimilation and other metabolic processes. We purified the gene product of facA (FacA) from the fungus to show that the fungus acetylates FacA on its lysine residue(s) specifically under conditions of ammonia fermentation to regulate its substrate affinity. Acetylated FacA had higher affinity for acetyl-CoA than for acetate, whereas non-acetylated FacA had more affinity for acetate. Thus, the acetylated variant of the FacA protein is responsible for ATP synthesis during fungal ammonia fermentation. These results showed that the fungus ferments ammonium via coupled dissimilatory and assimilatory mechanisms.
 ...
PMID:Fungal ammonia fermentation, a novel metabolic mechanism that couples the dissimilatory and assimilatory pathways of both nitrate and ethanol. Role of acetyl CoA synthetase in anaerobic ATP synthesis. 1472 82

Acetyl-coenzyme A (CoA) synthetase was purified 364-fold from leaves of spinach (Spinacia oleracea L.) using ammonium sulfate fractionation followed by ion exchange, dye-ligand, and gel permeation chromatography. The final specific activity was 2.77 units per milligram protein. The average M(r) value of the native enzyme was about 73,000. The Michaelis constants determined for Mg-ATP, acetate, and coenzyme A were 150, 57, and 5 micromolar, respectively. The purified enzyme was sensitive to substrate inhibition by CoA with an apparent K(i) for CoA of 700 micromolar. The enzyme was specific for acetate; other short and long chain fatty acids were ineffective as substrates. Several intermediates and end products of fatty acid synthesis were examined as potential inhibitors of acetyl-CoA synthetase activity, but none of the compounds tested significantly inhibited acetyl-CoA synthetase activity in vitro. The properties of the purified enzyme support the postulated role of acetyl-CoA synthetase as a primary source of chloroplast acetyl-CoA.
 ...
PMID:Spinach leaf acetyl-coenzyme a synthetase: purification and characterization. 1666 97

A general method for isotopic labeling of the purine base moiety of nucleotides and RNA has been developed through biochemical pathway engineering in vitro. A synthetic scheme was designed and implemented utilizing recombinant enzymes from the pentose phosphate and de novo purine synthesis pathways, with regeneration of folate, aspartate, glutamine, ATP, and NADPH cofactors, in a single-pot reaction. Syntheses proceeded quickly and efficiently in comparison to chemical methods with isolated yields up to 66% for 13C-, 15N-enriched ATP and GTP. The scheme is robust and flexible, requiring only serine, NH4+, glucose, and CO2 as stoichiometric precursors in labeled form. Using this approach, U-13C- GTP, U-13C, 15N- GTP, 13C 2,8- ATP, and U-15N- GTP were synthesized on a millimole scale, and the utility of the isotope labeling is illustrated in NMR spectra of HIV-2 transactivation region RNA containing 13C 2,8-adenosine and 15N 1,3,7,9,2-guanosine. Pathway engineering in vitro permits complex synthetic cascades to be effected, expanding the applicability of enzymatic synthesis.
ACS Chem Biol 2008 Aug 15
PMID:Pathway engineered enzymatic de novo purine nucleotide synthesis. 1870 56

Layered cesium tungstate, Cs(6+x)W(11)O(36), with two-dimensional (2D) pyrochlore structure was exfoliated into colloidal unilamellar sheets through a soft-chemical process. Interlayer Cs ions were replaced with protons by acid exchange, and quaternary ammonium ions were subsequently intercalated under optimized conditions. X-ray diffraction (XRD) measurements on gluelike sediment recovered from the colloidal suspension by centrifugation showed a broad pattern of a pronounced wavy profile, which closely matched the square of calculated structure factor for the single host layer. This indicates the total delamination of the layered tungstate into nanosheets of Cs(4)W(11)O(36)(2-). Microscopic observations by transmission electron microscopy and atomic force microscopy clearly revealed the formation of unilamellar crystallites with a very high 2D anisotropy, a thickness of only approximately 2 nm versus lateral size up to several micrometers. In-plane XRD analysis confirmed that the 2D pyrochlore structure was retained. The colloidal cesium tungstate nanosheet showed strong absorption of UV light with sharp onset, suggesting a semiconducting nature. Analysis of the absorption profile provided 3.6 eV as indirect band gap energy, which is 0.8 eV larger than that of the bulk layered precursor, probably due to size quantization. The nanosheet exhibited highly efficient photochromic properties, showing reversible color change upon UV irradiation.
ACS Nano 2008 Aug
PMID:Exfoliated nanosheet crystallite of cesium tungstate with 2D pyrochlore structure: synthesis, characterization, and photochromic properties. 1920 73

The synthesis and characterization of colloidal mesoporous silica (CMS) functionalized with vinyl-, benzyl-, phenyl-, cyano-, mercapto-, aminopropyl- or dihydroimidazole moieties is reported. Uniform mesoporous particles ranging in size from 40 to 150 nm are generated in a co-condensation process of tetraethylorthosilicate (TEOS) and organotriethoxysilanes (RTES) in alkaline aqueous media containing triethanolamine (TEA) in combination with cetyltrimethylammonium chloride (CTACl) serving as a structure-directing agent. The materials are obtained as colloidal suspensions featuring long-term stability after template removal by ion exchange with an ethanolic solution of ammonium nitrate or HCl. The spherical particles exhibit a wormlike pore system with defined pore sizes and high surface areas. Samples are analyzed by a number of techniques including TEM, SEM, DLS, TGA, Raman, and cross-polarized (29)Si-MAS NMR spectroscopy, as well as nitrogen sorption measurements. We demonstrate that co-condensation and grafting methods result in similar changes in the nitrogen adsorption behavior, indicating a successful internal lining of the pores with functional groups through both procedures.
ACS Nano 2008 Apr
PMID:Colloidal suspensions of functionalized mesoporous silica nanoparticles. 1920 12


1 2 3 4 5 6 7 8 9 10 Next >>