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showing 10 items of 2099 documents
Affinity Cleavage of Carbamoyl-Phosphate Synthetase I Localizes Regions of the Enzyme Interacting with the Molecule of ATP that Phosphorylates Carbam…
1995
Two ATP molecules are used in the reaction catalyzed by carbamoyl-phosphate synthetase I. One molecule (ATPA) phosphorylates HCO3- and the other (ATPB) phosphorylates carbamate. Carbamoyl-phosphate synthetase I is a 160-kDa polypeptide consisting of a 40-kDa N-terminal moiety and a 120-kDa C-terminal moiety, the latter being composed of two similar halves of molecular mass 60 kDa. We showed [Alonso, E., Cervera, J., Garcia-Espana, A., Bendala, E. & Rubio, V. (1992) J. Biol. Chem. 267, 4524-4532] that Fe.ATP bound at the site for ATPB catalyzes the oxidative inactivation of carbamoyl-phosphate synthetase I in a model oxidative system consisting of Fe3+, ascorbate, and O2, and we detected ATP…
Regulation of Farnesyl Diphosphate Synthase Gene Expression by Fatty Acids
2003
Cholesterol biosynthesis depends on the activity of regulatory enzymes, including the peroxisomal Farnesyl Diphosphate Synthase (FPPS ). Cholesterol regulates its own synthesis rate. Hence, as a response to cholesterol depletion, a feed back mechanism is activated, whereby sterol regulatory binding proteins (SREBPla, 1c and 2 ) are subjected to sequential proteolytic activation, which permits their interaction with specific DNA response elements from responsive genes. In turn, the transcriptional activity of cholesterol biosynthesis genes is induced. Conversely, cholesterol accumulation decreases SREBP maturation and transcription of controlled genes. In addition, polyunsaturated fatty acid…
Fermentbestimmungen in Erythrocyten von Kranken mit Porphyria cutanea tarda
1969
In Erythrocyten von 12 Kranken mit Porphyria cutanea tarda konnte eine Aktivitatssteigerung der Enzyme G-6-PDH, 6-PGDH sowie der NADH- und der NADPH-abhangigen Glutathionreduktion festgestellt werden, deren Ursache diskutiert wird.
Inorganic Polyphosphate in Eukaryotes: Enzymes, Metabolism and Function
1999
Inorganic polyphosphates (polyP) are linear polymers of orthophosphate (Pi) residues linked by high-energy phosphoanhydride bonds. These polymers are widely distributed in nature, from archaebacteria, eubacteria, fungi, algae, and protozoa to higher plants and animals (for reviews, see Kulaev 1979; Wood and Clark 1988; Kornberg 1994, 1995). PolyP molecules are stable in neutral aqueous solutions, but are hydrolyzed by heat-treatment, and under acidic or alkaline conditions. The chain length of polyP may range from 3 to more than 1000 Pi residues; it can be analyzed on urea/polyacrylamide gels (Clark and Wood 1987; Lorenz et al. 1994a). In contrast to the linear polymer, branched inorganic p…
Purification and characterization of an exopolyphosphatase from Saccharomyces cerevisiae.
1994
An exopolyphosphatase (polyphosphate phosphohydrolase; EC 3.6.1.11) activity that cleaves inorganic polyphosphates to orthophosphate has been purified to apparent homogeneity (> 95% pure) from Saccharomyces cerevisiae. The exopolyphosphatase is a monomeric protein with a polypeptide molecular mass of 28 kDa. The enzyme, which can be stabilized in the presence of Triton X-100, has a pH optimum of 7.5 and requires, for maximal activity, Co2+ or Mg2+ ions. In the absence of these ions, the exopolyphosphatase binds to polyphosphate but does not degrade it, allowing affinity purification of the enzyme on a polyphosphate-modified zirconia support. o-Vanadate, Cu2+, and Ca2+ are effective inhibito…
Cardenolides of Digitalis obscura: The effect of phosphate and manganese on growth and productivity of shoot-tip cultures
1997
Abstract Cardenolide composition of leaves from wild and micropropagated elite plants of Digitalis obscura (genotype T4) has been investigated and no qualitative differences were found among their major cardenolides (series A). All of the detected glycosides belong to the digitoxose-type cardenolides. Genins represented less than 2% of the overall content, while lanatoside A was the predominant cardenolide ( ca. 65%) in all samples. The cardenolide yield of micropropagated D. obscura plants depended on the age and development of the cultures, but productivity of long-term cultures (2 years) was quite similar to that of the parent plant. Changes in the concentrations of phosphate or manganes…
Discelectrophoretischer Nachweis der Heterogenität der menschlichen sauren Spermaphosphatase
2009
Zusammenfassung Mit Hilfe der vertikalen Discelektrophorese in Polyacrylamid-Gel ist es moglich, zwei Enzymbanden der sauren Spermaphosphatase nachzuweisen. Eine optimale Trennung ergibt sich bei einer Wasserstoffionenkonzentration von pH 7,5 im Trenn-Gel und pH 5,5 im Sammel-Gel und 0,1 M Acetatpuffer. Der Vorteil dieser Methode liegt in dem relativ geringen apparativen Aufwand, der kurzen Trennzeit, der hohen Trennscharfe sowie der Moglichkeit, aserst geringe Substanzmengen aufzutrennen. Summary With the aid of disc-electrophoresis in poly acryl amide it is possible to proof the heterogeneity of acid phosphatase of human seminal fluid. In all samples could be detected. The best results we…
When Chlorides are the Most Reactive: A Simple Route towards Diverse Mono- and Dicationic Dimethyl Phosphate Ionic Liquids
2014
Structurally diverse aromatic and aliphatic ionic liquids have been prepared via anion metathesis utilizing alkylammonium chlorides and trimethyl phosphate. Excellent oxygen-containing functional-group tolerance in preparation of potentially greener dimethyl phosphate ionic liquids has been demonstrated. For the first time, this method has been employed in the synthesis of dicationic imidazolium-based ionic liquids possessing a dimethyl phosphate counterion, providing a simple, direct route towards structurally novel products of high purity.
Studies on the interaction of phosphate anions with N-functionalised polyaza[n]paracyclophanes: the role of N-methylation.
2004
The synthesis and interaction of N,N',N'',N'''-tetramethyl-2,6,9,13-tetraaza[14]paracyclophanes (B323Me(4)) with nucleotides and inorganic phosphates is described. An easy methodology is used to define thermodynamic selectivity. The interaction of B323Me4 and ATP has been monitored by (1)H, (31)P NMR and by molecular mechanics, ruling out the possibility of the participation of pi-stacking interactions. Results show that N-methylation is accompanied by a strong increase in the interaction of the resulting macrocycle with ATP.
Metabolic integration in locust flight: the effect of octopamine on fructose 2,6-bisphosphate content of flight muscle in vivo
1994
The biogenic amine octopamine was injected into the haemolymph of 20-days old male locusts,Locusta migratoria, and the content of fructose 2,6-bisphosphate, a potent activator of glycolysis, was measured in the flight muscle after various time. Octopamine brought about a transient increase in fructose 2,6-bisphosphate. After the injection of 10 μl of 10 mmol·l-1 d, l-octopamine fructose 2,6-bisphosphate was increased by 61% within 2 min. Ten minutes after the injection fructose 2,6-bisphosphate was increased to 6.71±0.89 nmol·g-1 flight muscle, almost 300% over the control value. Flight caused fructose 2,6-bisphosphate in flight muscle to decrease, but this decrease was counteracted by octo…