scholarly journals Competitive, substrate-dependent reductive debromination/dehydrobromination of 1,2-dibromides with triethylamine

2017 ◽  
Vol 58 (20) ◽  
pp. 1973-1975 ◽  
Author(s):  
Kristen M. McGraw ◽  
Greggory T. Kent ◽  
Joseph R. Gonzalez ◽  
Ihsan Erden ◽  
Weiming Wu
Keyword(s):  
Competitive Substrate

Kinetics of Methane-Oxidizing Biofilms for Degradation of Toxic Organics

1988 ◽  
Vol 20 (11-12) ◽  
pp. 167-173 ◽  
Author(s):  
S. E. Strand ◽  
R. M. Seamons ◽  
M. D. Bjelland ◽  
H. D. Stensel
Keyword(s):  
Chlorinated Hydrocarbons ◽  
Enzymatic Oxidation ◽  
Diffusion Kinetics ◽  
Toxic Compound ◽  
Biofilm Model ◽  
Uptake Rates ◽  
Substrate Diffusion ◽  
Toxic Organics ◽  
Competitive Substrate ◽  
Kinetics Of

The kinetics of methane-oxidizing bioreactors for the degradation of toxic organics are modeled. Calculations of the fluxes of methane and toxic chlorinated hydrocarbons were made using a biofilm model. The model simulated the effects of competition by toxics and mediane on their enzymatic oxidation by the methane monooxygenase. Dual-competitive-substrate/diffusion kinetics were used to model biofilm co-metabolism, integrating equations of the following form:where S1 and S2 are the local concentrations of methane and toxic compound, respectively, and r and K are the maximum uptake rates and Monod coefficients, and x is the distance into the biofilm.

Gamma-glutamyltransferase: Substrate inhibition, kinetic mechanism, and assay conditions.

1976 ◽  
Vol 22 (4) ◽  
pp. 417-421 ◽  
Author(s):  
J H Stromme ◽  
L Theodorsen
Keyword(s):  
Clinical Chemistry ◽  
Substrate Inhibition ◽  
Kinetic Mechanism ◽  
Reaction Conditions ◽  
Gamma Glutamyltransferase ◽  
Gamma Glutamyl ◽  
Dead End ◽  
Ping Pong ◽  
Competitive Substrate ◽  
Assay Conditions

Abstract Gamma-glutamyltransferase activity in serum is shown to be competitively inhibited by the two substrates gamma-glutamyl-4-nitroanilide and glycylglycine. Awareness of this is of importance when one is choosing final reaction conditions for the assay of the enzyme. Gamma-glutamyltransferase probably acts by a "ping-pong bi-bi" kinetic mechanism, which fits with the double competitive substrate inhibition demonstrated. The product, 4-nitro-aniline, appears to be an uncompetitive dead-end inhibitor of both substrates. Various amino acids, particularly glycine and L-alanine, inhibit the enzyme. Their inhibition patterns are uncompetitive with glycylglycine and competitive with gamma-glutamyl-4-nitroanilide. On the basis of the present and other studies, the Scandinavian Society for Clinical Chemistry and Clinical Physiology is going to recommend for routine use a gamma-glutamyltransferase method in which the final concentrations of gamma-glutamyl-4-nitroanilide and glycylglycine are 4 and 75 mmol/liter, respectively.

Kinetic Characteristics, Substrate Specificity and Catalytic Properties of Phosphoserine Aminotransferase from the Green Alga Scenedesmus obliquus, Mutant C-2A

1995 ◽  
Vol 50 (9-10) ◽  
pp. 630-637 ◽  
Author(s):  
M. Stolz ◽  
D. Dörnemann
Keyword(s):  
Catalytic Properties ◽  
Scenedesmus Obliquus ◽  
Initial Reaction ◽  
Kinetic Characteristics ◽  
Forward Reaction ◽  
Phosphoserine Aminotransferase ◽  
Substrate Analogues ◽  
Ping Pong ◽  
The One ◽  
Competitive Substrate

Abstract Phosphoserine am inotransferase (EC 2.6.1.52) has been purified from Scenedesmus obliquus. mutant C -2A′, as reported previously (Stolz and Dörnemann, 1994). The current studies on its catalytic properties, involving initial reaction velocities as a function of the phosphoserine concentration at various fixed concentrations of 2-oxoglutarate as aminoacceptor, indicate a bi-bi ping pong mechanism . The application of a variety of substrate analogues of phosphoserine revealed no significant metabolisation of these com pounds and thus a considerable specificity of the enzyme. 4,5-dioxovalerate with glutamate as am inodonor is effective as competitive substrate to phosphohydroxypyruvate in the forward reaction and yields 5-am inolevulinate. 4.5-Dioxovalerate and glutam ate-1-semialdehyde can both serve as competitive aminoacceptor in the reverse reaction with phosphoserine and as substrate with 2-oxoglutarate as am inoacceptor. Comparison of the phosphoserine transamination with the transamination of 4,5-dioxovalerate revealed for both reactions a pH -optim um of 6 .8 -7 .0 in Mes/Bis-Trisbuffer. How ever, the Km-values and the Vmax for phosphoserine and 2-oxoglutarate on the one side, and 4,5-dioxovalerate and glutamate on the other were found to differ by orders of magnitude

On the Formation of Ultrathin Simox Structures by Low Energy Implantation

1992 ◽  
Vol 284 ◽  
Author(s):  
F. Namavar ◽  
B. Buchanan ◽  
N. M. Kalkhoran
Keyword(s):  
Integrated Circuits ◽  
Substrate Material ◽  
Low Energy ◽  
Silicon On Insulator ◽  
Great Promise ◽  
Ultrathin Layers ◽  
Commercial Applications ◽  
Competitive Substrate ◽  
The Cost ◽  
Radiation Hard

ABSTRACTSilicon-on-insulator (SOI) wafers made by standard energy (150–200 keV) Separation by IMplantation of Oxygen (SIMOX) processes have shown great promise for meeting the needs of radiation-hard microelectronics. However, if SIMOX material is to become a competitive substrate material for manufacturing commercial integrated circuits, the cost of the SIMOX wafers must be greatly reduced. The low energy SIMOX (LES) process accomplishes the needed reduction in cost by producing ultrathin layers which require much lower ion doses. These ultrathin layers are necessary for the next generation of commercial ultra high density CMOS integrated circuits, and must be of very high quality to be utilized for commercial applications. In this paper we discuss characterization of ultrathin LES structures.

scholarly journals Competitive Substrate Binding Coordinates the Two Antagonistic Motors of the Bacterial Type IV Pilus

2020 ◽  
Vol 118 (3) ◽  
pp. 128a
Author(s):  
Matthias D. Koch ◽  
Chenyi Fei ◽  
Ned S. Wingreen ◽  
Zemer Gitai ◽  
Joshua W. Shaevitz
Keyword(s):  
Substrate Binding ◽  
Type Iv Pilus ◽  
Type Iv ◽  
Competitive Substrate ◽  
Bacterial Type

Probing prime substrate binding sites of human dipeptidyl peptidase-IV using competitive substrate approach

2005 ◽  
Vol 436 (2) ◽  
pp. 367-376 ◽  
Author(s):  
Lisa M. Kopcho ◽  
Young B. Kim ◽  
Aiying Wang ◽  
Margaret A. Liu ◽  
Mark S. Kirby ◽  
...  
Keyword(s):  
Binding Sites ◽  
Substrate Binding ◽  
Dipeptidyl Peptidase ◽  
Dipeptidyl Peptidase Iv ◽  
Competitive Substrate ◽  
Substrate Binding Sites

Hyperoxia increases H2O2 production by brain in vivo

1987 ◽  
Vol 63 (1) ◽  
pp. 353-358 ◽  
Author(s):  
T. Yusa ◽  
J. S. Beckman ◽  
J. D. Crapo ◽  
B. A. Freeman
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Catalase Activity ◽  
Intermediate Compound ◽  
H2o2 Production ◽  
H2o2 Concentration ◽  
Compound I ◽  
Central Nervous System Toxicity ◽  
Competitive Substrate

Hyperoxia and hyperbaric hyperoxia increased the rate of cerebral hydrogen peroxide (H2O2) production in unanesthetized rats in vivo, as measured by the H2O2-mediated inactivation of endogenous catalase activity following injection of 3-amino-1,2,4-triazole. Brain catalase activity in rats breathing air (0.2 ATA O2) decreased to 75, 61, and 40% of controls due to endogenous H2O2 production at 30, 60, and 120 min, respectively, after intraperitoneal injection of 3-amino-1,2,4-triazole. The rate of catalase inactivation increased linearly in rats exposed to 0.6 ATA O2 (3 ATA air), 1.0 ATA O2 (normobaric 100% O2) and 3.0 ATA O2 (3 ATA 100% O2) compared with 0.2 ATA O2 (room air). Catalase inactivation was prevented by pretreatment of rats with ethanol (4 g/kg), a competitive substrate for the reactive catalase-H2O2 intermediate, compound I. This confirmed that catalase inactivation by 3-amino-1,2,4-triazole was due to formation of the catalase-H2O2 intermediate, compound I. The linear rate of catalase inactivation allows estimates of the average steady-state H2O2 concentration within brain peroxisomes to be calculated from the formula: [H2O2] = 6.6 pM + 5.6 ATA-1 X pM X [O2], where [O2] is the concentration of oxygen in ATA that the rats are breathing. Thus the H2O2 concentration in brains of rats exposed to room air is calculated to be about 7.7 pM, rises 60% when O2 tension is increased to 100% O2, and increases 300% at 3 ATA 100% O2, where symptoms of central nervous system toxicity first become apparent. These studies support the concept that H2O2 is an important mediator of O2-induced injury to the central nervous system.

scholarly journals Release of Ca2+ from intracellular organelles by peptide analogues: evidence against involvement of metalloendoproteases in Ca2+ sequestration by the endoplasmic reticulum

1994 ◽  
Vol 304 (2) ◽  
pp. 499-507 ◽  
Author(s):  
M A Brostrom ◽  
W L Wong Ling ◽  
D Gmitter ◽  
C O Brostrom
Keyword(s):  
Endoplasmic Reticulum ◽  
Ryanodine Receptors ◽  
Pituitary Cells ◽  
Peptide Bonds ◽  
High Affinity ◽  
Synthesis And Processing ◽  
Internal Peptide ◽  
Competitive Substrate ◽  
Nitrophenyl Ester ◽  
Peptide Analogues

N-Benzyloxycarbonyl-Gly-Phe-amide (Z-Gly-Phe-NH2), a competitive substrate for metalloendoproteases, mobilizes intracellular Ca2+ and suppresses protein synthesis and processing in a Ca(2+)-dependent, reversible manner. To ascertain whether Z-Gly-Phe-NH2 acts as Ca(2+)-storing organelles, effects of the dipeptide on Ca2+ sequestration by saponin-porated GH3 pituitary cells were examined. Porated preparations sequestered Ca2+ into two compartments with different Ca2+ affinities. Ca2+ accumulation at nM concentrations of free Ca2+ was inhibited by thapsigargin and inositol 1,4,5-triphosphate [Ins(1,4,5)P3], enhanced by oxalate and unaffected by oligomycin. Cation accumulation at microM concentrations of free Ca2+ was sensitive to oligomycin but not to thapsigargin. Z-Gly-Phe-NH2 reduced Ca2+ sequestration by both compartments. The dipeptide mobilized Ca2+ from the high-affinity compartment within 1-2 min without affecting Ca2+ uptake. Ca2+ was mobilized more rapidly by Z-Gly-Phe-NH2 and thapsigargin together than by either agent alone. The presence of a thiol-reducing agent was required for Ca2+ mobilization by Z-Gly-Phe-NH2 but not by thapsigargin or Ins(1,4,5)P3. Ca2+ mobilization by Z-Gly-Phe-NH2 could not be attributed to effects on anion-permeability or to actions at Ins(1,4,5)P3 or ryanodine receptors. Results with assorted peptide analogues did not favour suppression of metalloendoprotease activity in the Ca(2+)-mobilizing action of Z-Gly-Phe-NH2. The more hydrophobic analogue Z-L-Tyr-p-nitrophenyl ester was 60-80-fold more potent in mobilizing Ca2+ from intact and porated cells and perturbed the high-affinity Ca(2+)-sequestering compartment selectively. Z-Gly-Phe-NH2 and Z-L-Tyr-p-nitrophenyl ester are proposed to release Ca2+ from the endoplasmic reticulum through an ion pore with affinity for hydrophobic molecules containing internal peptide bonds.

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