Kinetics of competitive inhibition and cometabolism in the biodegradation of benzene, toluene, andp-xylene by twoPseudomonasisolates.

1993 ◽  
Vol 41 (11) ◽  
pp. 1057-1065 ◽  
Author(s):  
Myung-Keun Chang ◽  
Thomas C. Voice ◽  
Craig S. Criddle
Keyword(s):  
Competitive Inhibition ◽  
Benzene Toluene ◽  
Kinetics Of

Kinetic Aspects of the Interaction of Blood Clotting Enzymes

1968 ◽  
Vol 19 (03/04) ◽  
pp. 364-367 ◽  
Author(s):  
H. C Hemker ◽  
P. W Hemker
Keyword(s):  
Enzyme Kinetics ◽  
Blood Clotting ◽  
Competitive Inhibition ◽  
Competitive Inhibitor ◽  
Kinetics Of

SummaryThe enzyme kinetics of competitive inhibition under conditions prevailing in clotting tests are developed and a method is given to measure relative amounts of a competitive inhibitor by means of the t — D plot.

The Kinetics of Inhibition of the Action of Thrombin by the Fibrinopeptides Formed during the Clotting of Fibrinogen

1966 ◽  
Vol 16 (01/02) ◽  
pp. 277-295 ◽  
Author(s):  
A Silver ◽  
M Murray
Keyword(s):  
Amino Acids ◽  
Competitive Inhibition ◽  
Amorphous Material ◽  
Peptide Bond ◽  
Initial Reaction ◽  
Reaction Products ◽  
Coagulation Mechanism ◽  
Kinetics Of ◽  
Kinetics Of Inhibition ◽  
Burk Plot

SummaryVarious investigators have separated the coagulation products formed when fibrinogen is clotted with thrombin and identified fibrinopeptides A and B. Two other peaks are observed in the chromatogram of the products of coagulation, but these have mostly been dismissed by other workers. They have been identified by us as amino acids, smaller peptides and amorphous material (37). We have re-chromatographed these peaks and identified several amino acids. In a closed system of fibrinogen and thrombin, the only reaction products should be fibrin and peptide A and peptide B. This reasoning has come about because thrombin has been reported to be specific for the glycyl-arginyl peptide bond. It is suggested that thrombin also breaks other peptide linkages and the Peptide A and Peptide B are attacked by thrombin to yield proteolytic products. Thrombin is therefore probably not specific for the glycyl-arginyl bond but will react on other linkages as well.If the aforementioned is correct then the fibrinopeptides A and B would cause an inhibition with the coagulation mechanism itself. We have shown that an inhibition does occur. We suggest that there is an autoinhibition to the clotting mechanism that might be a control mechanism in the human body.The experiment was designed for coagulation to occur under controlled conditions of temperature and time. Purified reactants were used. We assembled an apparatus to record visually the speed of the initial reaction, the rate of the reaction, and the density of the final clot formed after a specific time.The figures we derived made available to us data whereby we could calculate and plot the information to show the mechanism and suggest that such an inhibition does exist and also further suggest that it might be competitive.In order to prove true competitive inhibition it is necessary to fulfill the criteria of the Lineweaver-Burk plot. This has been done. We have also satisfied other criteria of Dixon (29) and Bergman (31) that suggest true competitive inhibition.

scholarly journals The combustion of aromatic and alicyclic hydrocarbons. II. The ignition of aromatic hydrocarbons at high temperatures

1939 ◽  
Vol 171 (946) ◽  
pp. 421-433 ◽  
Keyword(s):  
High Temperatures ◽  
Aromatic Hydrocarbons ◽  
Isothermal Oxidation ◽  
Present Communication ◽  
Temperature Range ◽  
Benzene Toluene ◽  
The Subject ◽  
Kinetics Of

In the first paper of this series (Burgoyne 1937) the kinetics of the isothermal oxidation above 400° C of several aromatic hydrocarbons was studied. The present communication extends this work to include the phenomena of ignition in the same temperature range, whilst the corresponding reactions below 400° C form the subject of further investigations now in progress. The hydrocarbons at present under consideration are benzene, toluene, ethylbenzene, n -propylbenzene, o-, m - and p -xylenes and mesitylene.

scholarly journals Mitochondrial adenosine triphosphatase from human placenta--inhibition by free magnesium ions of ITP hydrolysis.

1994 ◽  
Vol 41 (1) ◽  
pp. 39-44 ◽  
Author(s):  
Z Aleksandrowicz
Keyword(s):  
Competitive Inhibition ◽  
Competitive Inhibitor ◽  
Hill Coefficient ◽  
Negative Cooperativity ◽  
Magnesium Ions ◽  
Beef Liver ◽  
Bicarbonate Ions ◽  
The Hill ◽  
Kinetics Of ◽  
Free Magnesium

The effects of Mg2+ and bicarbonate on the kinetics of ITP hydrolysis by soluble ATPase (F1) from human placental mitochondria were studied. Increasing amounts of Mg2+ at fixed ITP concentration, caused a marked activation of F1 followed by inhibition at higher Mg2+ concentration. The appropriate substrate for the mitochondrial F1 seems to be the MgITP complex as almost no ITP was hydrolysed in the absence of magnesium. Mg2+ behaved as a competitive inhibitor towards the MgITP complex. In this respect the human placental enzyme differ from that from other sources such as yeast, beef liver or rat liver. The linearity of the plot presenting competitive inhibition by free Mg2+ of MgITP hydrolysis (in the presence of activating bicarbonate anion) suggests that both Mg2+ and MgITP bind to the same catalytic site (Km(MgITP) = 0.46 mM, Ki(Mg) = 4 mM). When bicarbonate was absent in the ITPase assay, placental F1 exhibited apparent negative cooperativity in the presence of 5 mM Mg2+, just as it did with MgATP as a substrate under similar conditions. Bicarbonate ions eliminated the negative cooperativity with respect to ITP (as the Hill coefficient of 0.46 was brought to approx. 1), and thus limited inhibition by free Mg2+. The results presented suggest that the concentration of free magnesium ions may be an important regulatory factor of the human placental F1 activity.

Biodegradation and Growth Kinetics of Enrichment Isolates on Benzene, Toluene and Xylene

1988 ◽  
Vol 20 (11-12) ◽  
pp. 505-507 ◽  
Author(s):  
C. D. Goldsmith ◽  
Russell K. Balderson
Keyword(s):  
Growth Kinetics ◽  
Benzene Toluene ◽  
Kinetics Of

Kinetics of the deep oxidation of benzene, toluene, n-hexane and their binary mixtures over a platinum on γ-alumina catalyst

2002 ◽  
Vol 38 (2) ◽  
pp. 139-149 ◽  
Author(s):  
Salvador Ordóñez ◽  
Lisardo Bello ◽  
Herminio Sastre ◽  
Roberto Rosal ◽  
Fernando V. Dı́ez
Keyword(s):  
Binary Mixtures ◽  
Deep Oxidation ◽  
Alumina Catalyst ◽  
Benzene Toluene ◽  
Kinetics Of ◽  
Oxidation Of Benzene

Kinetics of azoreductase and assessment of toxicity of metabolic products from azo dyes by Pseudomonas luteola

2001 ◽  
Vol 43 (2) ◽  
pp. 261-269 ◽  
Author(s):  
T.-L. Hu
Keyword(s):  
Azo Dyes ◽  
Competitive Inhibition ◽  
Orthanilic Acid ◽  
Metabolic Products ◽  
Before And After ◽  
Ft Ir ◽  
Ir Analysis ◽  
Pseudomonas Luteola ◽  
Monoazo Dyes ◽  
Kinetics Of

This is a continuous study on a decolorization strain, Pseudomonas luteola, which involves treating seven azo dyes with different structures. This study focuses mainly on determining both the mechanism of decolorization by P. luteola and the activity of azoreductase from P. luteola as well as identifying and assessing the toxicity of metabolic products of azo dyes. The growth of P. luteola reached the stationary phase after shaking incubation for 24 hours. Then, while being kept static, the color of seven tested azo dyes (100 mg/l) could be removed. The proportion of color removal was between 59–99%, which figure is related to the structure of the dye. Monoazo dyes (RP2B, V2RP and Red 22) showed the fastest rate of decolorization, i.e. from 0.23–0.44 mg dye-mg cell–1 hr–1. P. luteola could remove the color of V2RP and a leather dye at a concentration of 200 mg/l, and as to the rest of the azo dyes, it could remove at a concentration of up to 100 mg/l. Decolorization of RP2B and Red 22 required activation energy of 7.00 J/mol and 6.63 J/mole, respectively, indicating that it was easier for azoreductase to decolorize structurally simple dyes. The kinetics of azoreductase towards seven azo dyes suggested a competitive inhibition model be applied. Microtox® was used to analyze the toxicity of the metabolic products of azo dyes. EC50 showed differences in toxicity before and after the azo dyes had been metabolized. Analysis revealed significant differences between the results obtained by EC50 with Blue 15 and those obtained with the leather dye, indicating that the toxicities of the metabolic products were increased. The differences obtained by EC50 with Red 22, RP2P and V2RP were small, and Black 22 showed no such difference. Sulfanic acid and orthanilic acid may be the intermediate products of Violet 9 and RP2B, respectively. However, according to FT-IR analysis, aromatic amines were present in the metabolic product.

Biodegradation kinetics of BTE-OX and MTBE by a diesel-grown biomass

2006 ◽  
Vol 53 (11) ◽  
pp. 197-204 ◽  
Author(s):  
K. Acuna-Askar ◽  
M.A. de la Torre-Torres ◽  
M.J. Guerrero-Munoz ◽  
M.T. Garza-Gonzalez ◽  
B. Chavez-Gomez ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Removal Rate ◽  
Biodegradation Kinetics ◽  
Aqueous Samples ◽  
Removal Rates ◽  
Two Phase ◽  
Bacterial Populations ◽  
Substrate Removal ◽  
Benzene Toluene ◽  
Kinetics Of

The biodegradation kinetics of BTE-oX and MTBE, mixed all together in the presence of diesel-grown bioaugmented bacterial populations as high as 885 mg/L VSS, was evaluated. The effect of soil in aqueous samples and the effect of Tergitol NP-10 on substrate biodegradation rates were also evaluated. Biodegradation kinetics was evaluated for 54 h, every 6 h. All BTE-oX chemicals followed a first-order two-phase biodegradation kinetic model, whereas MTBE followed a zero-order removal kinetic model in all samples. BTE-oX removal rates were much higher than those of MTBE in all samples. The presence of soil in aqueous samples retarded BTE-oX and MTBE removal rates. The addition of Tergitol NP-10 to aqueous samples containing soil had a positive effect on substrate removal rate in all samples. Substrate percent removals ranged between 64.8–98.9% for benzene, toluene and ethylbenzene. O-xylene and MTBE percent removals ranged between 18.7–40.8% and 7.2–10.3%, respectively.

Phase-plane geometries in enzyme kinetics

1994 ◽  
Vol 72 (3) ◽  
pp. 800-812 ◽  
Author(s):  
Simon J. Fraser ◽  
Marc R. Roussel
Keyword(s):  
Steady State ◽  
Phase Plane ◽  
Competitive Inhibition ◽  
Three Dimensional ◽  
Product Inhibition ◽  
Slow Manifold ◽  
Dimensional System ◽  
Planar System ◽  
State Behaviour ◽  
Kinetics Of

The transient and steady-state behaviour of the reversible Michaelis–Menten mechanism [R] and Competitive Inhibition (CI) mechanism is studied by analysis in the phase plane. Usually, the kinetics of both mechanisms is simplified to give a modified Michaelis–Menten velocity expression; this applies to the CI mechanism with excess inhibitor and to mechanism [R] in the product inhibition limit. In this paper, [R] is treated exactly as a plane autonomous system of differential equations and its true (dynamical) steady state is described by a line-like slow manifold M. Initial velocity experiments for [R] no longer strictly correspond to the hyperbolic law (as in the irreversible Michaelis–Menten mechanism) and this leads to corrections to the standard integrated rate law. Using a new analysis, the slow dynamics of the CI mechanism is reduced from a three-dimensional system to a planar system. In this mechanism transient decay collapses the trajectory flow onto a two-dimensional "slow" surface Σ; motion on Σ can be treated exactly as projected dynamics in the plane. This projected flow may differ in important ways from that of two-step mechanisms, e.g., it may lack a proper steady state. The relevance of these more accurate dynamical descriptions is discussed in relation to experimental design and metabolic function.

scholarly journals Kinetic and e.p.r. studies of cyanide and azide binding to the copper sites of dopamine (3,4-dihydroxyphenethylamine) β-mono-oxygenase

1984 ◽  
Vol 220 (2) ◽  
pp. 447-454 ◽  
Author(s):  
N J Blackburn ◽  
D Collison ◽  
J Sutton ◽  
F E Mabbs
Keyword(s):  
Competitive Inhibition ◽  
Charge Transfer Band ◽  
The Other ◽  
Native Enzyme ◽  
Interacting Species ◽  
Other Hand ◽  
Show Evidence ◽  
Simultaneous Decrease ◽  
Copper Sites ◽  
Kinetics Of

The kinetics of inhibition of dopamine (3,4-dihydroxyphenethylamine) beta-mono-oxygenase by cyanide (CN-) and azide (N3-) ions have been investigated by using steady-state methods. Both anions show complex non-competitive-inhibition patterns with respect to ascorbate, suggestive of anion binding at two different sites on the oxidized enzyme. To further investigate this finding, e.p.r. titrations of CN- and N3- binding to the 63Cu-reconstituted enzyme were carried out. Addition of approx. 2 equiv. of CN- to copper elicits a new signal with g = 2.217, g = 2.025, A = 17.0 mT characteristic of a copper (II)-cyano complex. Simulations show that this signal accounts for half the copper (II) in the enzyme. The remainder of the enzyme-bound copper is expressed by a signal close to, but not identical with, that of native enzyme. Further addition of CN- induces a simultaneous decrease in intensity of both of these signals so that their 1:1 ratio is maintained. Binding of N3-, on the other hand, changes the e.p.r. spectrum to a form different from either that of the native or CN‒ -treated enzyme, and integrates to 100% of the copper in the enzyme (g = 2.252, g = 2.050, A = 16.5 mT). Resolved superhyperfine structure is apparent in the g region. N3- binding is also accompanied by the appearance of a broad charge-transfer band centred at 387 nm. Neither 9 nor 35 GHz e.p.r. spectra show evidence for more than one (non-interacting) species of Cu(II) in native enzyme and N3- derivatives. The binding and reactivity of CN-, on the other hand, argues against independent copper sites in the enzyme.

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