scholarly journals Catalytic irreversible inhibition of bacterial and plant arginine decarboxylase activities by novel substrate and product analogues

1987 ◽  
Vol 242 (1) ◽  
pp. 69-74 ◽  
Author(s):  
A J Bitonti ◽  
P J Casara ◽  
P P McCann ◽  
P Bey
Keyword(s):  
Arginine Decarboxylase ◽  
Irreversible Inhibitor ◽  
Polyamine Biosynthesis ◽  
E Coli ◽  
First Order ◽  
Irreversible Inhibition ◽  
First Order Kinetics ◽  
Low Concentrations ◽  
Pseudo First Order

Arginine decarboxylase (ADC) activity from Escherichia coli and two plant species (oats and barley) was inhibited by five new substrate (arginine) and product (agmatine) analogues. The five compounds, (E)-alpha-monofluoromethyldehydroarginine (delta-MFMA), alpha-monofluoromethylarginine (MFMA), alpha-monofluoromethylagatine (FMA), alpha-ethynylagmatine (EA) and alpha-allenylagmatine (AA), were all more potent inhibitors of ADC activity than was alpha-difluoromethylarginine (DFMA), the only irreversible inhibitor of this enzyme described previously. The inhibition caused by the five compounds was apparently enzyme-activated and irreversible, since the loss of enzyme activity followed pseudo-first-order kinetics, was time-dependent, the natural substrate of ADC (arginine) blocked the effects of the inhibitors, and the inhibition remained after chromatography of inhibited ADC on Sephadex G-25 or on overnight dialysis of the enzyme. DFMA, FMA, delta-MFMA and MFMA were effective at very low concentrations (10 nM-10 microM) at inhibiting ADC activity in growing E. coli. FMA was also shown to deplete putrescine effectively in E. coli, particularly when combined with an inhibitor of ornithine decarboxylase, alpha-monofluoromethyl-putrescine. The potential uses of the compounds for the study of the role of polyamine biosynthesis in bacteria and plants is discussed.

scholarly journals The role of histidine-118 of inorganic pyrophosphatase from thermophilic bacterium PS-3

1991 ◽  
Vol 278 (2) ◽  
pp. 595-599 ◽  
Author(s):  
N Hirano ◽  
T Ichiba ◽  
A Hachimori
Keyword(s):  
Thermophilic Bacterium ◽  
Complete Loss ◽  
Inorganic Pyrophosphatase ◽  
Histidine Residue ◽  
First Order ◽  
Diethyl Pyrocarbonate ◽  
Lysyl Endopeptidase ◽  
First Order Kinetics ◽  
Pseudo First Order

Treatment of the inorganic pyrophosphatase from thermophilic bacterium PS-3 with diethyl pyrocarbonate resulted in the almost complete loss of its activity, which followed pseudo-first-order kinetics. The presence of Mg2+ prevented the inactivation. Enzyme inactivated with diethyl pyrocarbonate was re-activated by hydroxylamine. The inactivation parallelled the amount of modified histidine residue, and a plot of the activity remaining against the amount of modified histidine residue suggested that the modification of one of two histidine residues totally inactivated the enzyme. The site involved was found to be located in a single lysyl endopeptidase-digest peptide derived from the ethoxy[14C]carbonylated enzyme. Amino acid analysis and sequence analysis of the peptide revealed that it comprised residues 96-119 of the inorganic pyrophosphatase from thermophilic bacterium PS-3. These results, when compared with those reported for the Escherichia coli and yeast enzymes, imply that His-118 of the inorganic pyrophosphatase from thermophilic bacterium PS-3 is located near the Mg(2+)-binding site and thus affects the binding of Mg2+.

Role of pH on Metribuzin Dissipation in Field Soils

Weed Science ◽  
1976 ◽  
Vol 24 (5) ◽  
pp. 508-511 ◽  
Author(s):  
James S. Ladlie ◽  
William F. Meggitt ◽  
Donald Penner
Keyword(s):  
Soil Ph ◽  
Half Life ◽  
Residue Analysis ◽  
Soil Samples ◽  
First Order ◽  
First Order Kinetics ◽  
Field Soils ◽  
Pseudo First Order

Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] residue analysis of soil samples showed greater amounts of residue extractable at soil pH 6.7 than 4.6. Metribuzin leaching increased with increasing soil pH. Metribuzin disappearance from soil followed pseudo first-order kinetics. The half-life of metribuzin decreased as soil pH increased and increased at all soil pH levels as depth of sampling increased. The decreased activity and decreased rate of metribuzin dissipation at lower soil pH is apparently due to protonation and increased adsorption.

scholarly journals Exploring the scope of DBU-promoted amidations of 7-methoxycarbonylpterin

2020 ◽  
Vol 16 ◽  
pp. 509-514 ◽  
Author(s):  
Anna R Bockman ◽  
Jeffrey M Pruet
Keyword(s):  
Reaction Kinetics ◽  
Structural Features ◽  
Product Formation ◽  
Reaction Conditions ◽  
First Order ◽  
First Order Kinetics ◽  
Synthetic Utility ◽  
Pseudo First Order ◽  
Pteridine Derivatives

The synthetic utility of pterins is often hampered by the notorious insolubility of this heterocycle, slowing the development of medicinally relevant pteridine derivatives. Reactions which expedite the development of new pterins are thus of great importance. Through a dual role of diazabicycloundecene (DBU), 7-carboxymethylpterin is converted to the soluble DBU salt, with additional DBU promoting an ester-to-amide transformation. We have explored this reaction to assess its scope and identify structural features in the amines which significantly affect success, monitored the reaction kinetics using a pseudo-first order kinetics model, and further adapted the reaction conditions to allow for product formation in as little as 5 min, with yields often >80%.

Active-site-directed inactivation of Schizophyllum commune cellulase by 4′, 5′-epoxypentyl-4-D-(β-D-glucopyranosyl)-β-D-glucopyranoside

1988 ◽  
Vol 66 (8) ◽  
pp. 871-879 ◽  
Author(s):  
Anthony John Clarke
Keyword(s):  
Active Site ◽  
Schizophyllum Commune ◽  
Competitive Inhibitor ◽  
Irreversible Inhibitor ◽  
Inhibitor Molecule ◽  
Enzyme Active Site ◽  
First Order ◽  
First Order Kinetics ◽  
Pseudo First Order ◽  
Inactivation Process

4′,5′-Epoxypentyl-4-D-(β-D-glucopyranosyl)-β-D-glucopyranoside (4) was synthesized by a Koenigs–Knorr reaction of 4-penten-1-ol and acetobromcellobiose, promoted by silver trifluoromethanesulfonate and N,N′-tetramethylurea, and tested as a potential active-site-directed irreversible inhibitor of the Schizophyllum commune cellulase. Incubation of the S. commune cellulase with 4 resulted in a time-dependent irreversible inactivation of the enzyme. The inactivation process obeyed pseudo-first-order kinetics and the hyperbolic plot of kobs as a function of inhibitor concentration provided values for Kd and k2 of 150 mM and 2.0 × 10−4 s−1, respectively, at pH 5.5 and 25 °C. The binding of a competitive inhibitor, cellobiose, to the cellulase prior to incubation with 4 protected the enzyme from rapid inactivation, suggesting that the inactivation is due to attack at the active site. The dependence of the inactivation on pH is consistent with the participation of carboxyl groups. Treatment of the affinity-labeled enzyme with [14C]methoxyamine resulted in the near stoichiometric formation of a stable radiolabelled adduct, suggesting that one inhibitor molecule binds per enzyme active site of the enzyme.

Inhibition of E. coli ʟ-Asparaginase by Reaction with 2,3-Butanedione. Chemical Modification of Arginine and Histidine Residues

1979 ◽  
Vol 34 (9-10) ◽  
pp. 742-746 ◽  
Author(s):  
Dorothee Petz ◽  
Hans-Gerhard Löffler ◽  
Friedh. Schneider
Keyword(s):  
Chemical Modification ◽  
Histidine Modification ◽  
Histidine Residues ◽  
E Coli ◽  
First Order ◽  
Complete Inactivation ◽  
First Order Kinetics ◽  
Competitive Inhibitors ◽  
Pseudo First Order

Abstract The inactivation of E. coli asparaginase by 2,3-butanedione studied with ʟ-asparagine and diazooxonorvaline as substrates obeys pseudo first order kinetics. Activity losses are linear with respect to arginine and histidine modification, with complete inactivation being correlated with alteration of one arginine and one histidine per subunit. The rate of inactivation of the enzym was reduced in the presence of competitive inhibitors like ʟ-2-amino-2-carboxyethane-sulfonamide. Un der comparable conditions 1,2-cyclo hexanedione does not affect the activity of ʟ-asparaginase.

scholarly journals Active-site-directed irreversible inhibition of rat brain 4-aminobutyrate aminotransferase by ethanolamine O-sulphate in vitro and in vivo

1972 ◽  
Vol 130 (2) ◽  
pp. 569-573 ◽  
Author(s):  
L. J. Fowler ◽  
R. A. John
Keyword(s):  
Rat Brain ◽  
Dependent Manner ◽  
Aminobutyrate Aminotransferase ◽  
First Order ◽  
Irreversible Inhibition ◽  
First Order Kinetics ◽  
Intracisternal Injection ◽  
Pseudo First Order

1. Partially purified preparations of rat brain 4-aminobutyrate aminotransferase were inhibited in a time-dependent manner by ethanolamine O-sulphate. The inhibition was not reversed by dialysis. 2. The inhibitor formed an initial reversible complex with the enzyme (Ki=4.4×10−4m) and the rate of inactivation followed pseudo-first-order kinetics (k=7.15×10−4s−1). The inclusion of 4-aminobutyrate markedly slowed the rate of inactivation. 3. Ethanolamine O-sulphate did not inhibit glutamate decarboxylase, alanine aminotransferase or aspartate aminotransferase. 4. Intracisternal injection of ethanolamine O-sulphate into rats led to rapid inactivation of 4-aminobutyrate aminotransferase in vivo.

Enzymatic Nitrate Assay by a Kinetic Method Employing Escherichia coli Nitrate Reductase

1985 ◽  
Vol 40 (1-2) ◽  
pp. 134-137 ◽  
Author(s):  
Johannes Schild ◽  
Jobst-Heinrich Klemme
Keyword(s):  
Nitrate Reductase ◽  
Reaction Rate ◽  
Kinetic Method ◽  
Test System ◽  
Enzymatic Assay ◽  
E Coli ◽  
First Order ◽  
First Order Kinetics ◽  
Membrane Bound ◽  
Pseudo First Order

Abstract An enzymatic assay system for nitrate employing the membrane-bound nitrate reductase (EC 1.7.99.4) of E. coli is described. Contrary to previous enzymatic assay systems, the present method is a kinetic one, i.e. the substrate, nitrate, is assayed by measuring the reaction rate of the nitrate reductase-catalyzed reaction. Based on the observation that the nitrate reductase-catalyzed reaction obeys pseudo-first order kinetics, a test system is described allowing the assay of nitrate at a concentration as low as 1 ppm. The relatively high M ichaelis-M enten constant for nitrate (0.3 mᴍ) of the E. coli nitrate reductase favours nitrate assay by the kinetic method.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah
Keyword(s):  
Half Life ◽  
Hplc Method ◽  
Hydrolysis Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Rp Hplc ◽  
Pharmacokinetic Properties ◽  
Pseudo First Order ◽  
Kinetic Hydrolysis

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.

scholarly journals Ganglioside incorporation and release by the isolated perfused rat liver

1991 ◽  
Vol 274 (2) ◽  
pp. 581-585 ◽  
Author(s):  
S C Kivatinitz ◽  
A Miglio ◽  
R Ghidoni
Keyword(s):  
Rat Liver ◽  
The Other ◽  
Regulatory Role ◽  
Isolated Perfused Rat Liver ◽  
Order Kinetic ◽  
Perfused Rat Liver ◽  
Ganglioside Gm1 ◽  
First Order ◽  
Pseudo First Order

The fate of exogenous ganglioside GM1 labelled in the sphingosine moiety, [Sph-3H]GM1, administered as a pulse, in the isolated perfused rat liver was investigated. When a non-recirculating protocol was employed, the amount of radioactivity in the liver and perfusates was found to be dependent on the presence of BSA in the perfusion liquid and on the time elapsed after the administration of the ganglioside. When BSA was added to the perfusion liquid, less radioactivity was found in the liver and more in the perfusate at each time tested, for up to 1 h. The recovery of radioactivity in the perfusates followed a complex course which can be described by three pseudo-first-order kinetic constants. The constants, in order of decreasing velocity, are interpreted as: (a) the dilution of the labelled GM1 by the constant influx of perfusion liquid; (b) the washing off of GM1 loosely bound to the surface of liver cells; (c) the release of gangliosides from the liver. Process (b) was found to be faster in the presence of BSA, probably owing to the ability of BSA to bind gangliosides. The [Sph-3H]GM1 in the liver underwent metabolism, leading to the appearance of products of anabolic (GD1a, GD1b) and catabolic (GM2, GM3) origin; GD1a appeared before GM2 and GM3 but, at times longer than 10 min, GM2 and GM3 showed more radioactivity than GD1a. At a given time the distribution of the radioactivity in the perfusates was quite different from that of the liver. In fact, after 60 min GD1a was the only metabolite present in any amount, the other being GM3, the quantity of which was small. This indicates that the liver is able to release newly synthesized gangliosides quite specifically. When a recirculating protocol was used, there were more catabolites and less GD1a than with the non-recirculating protocol. A possible regulatory role of ganglioside re-internalization on their own metabolism in the liver is postulated.

Sign in / Sign up

Export Citation Format

Share Document