Kinetic properties of 7α-hydroxysteroid dehydrogenase from Escherichia coli 080

1989 ◽  
Vol 35 (12) ◽  
pp. 1076-1080 ◽  
Author(s):  
V. Prabha ◽  
Meenakshi Gupta ◽  
K. G. Gupta
Keyword(s):  
Escherichia Coli ◽  
Bile Acids ◽  
Sodium Perchlorate ◽  
Tween 80 ◽  
Thiol Group ◽  
Hydroxysteroid Dehydrogenase ◽  
Enzyme Concentration ◽  
Tween 20 ◽  
Kinetic Properties ◽  
Potassium Oxalate

Results on the kinetics of 7α-hydroxysteroid dehydrogenase 7α-HSDH showed that this enzyme could oxidize all bile acids having an –OH group at the C-7 position. Lineweaver-Burk plots showed Michaelis constant (Km) values of 0.83 and 0.12 mM for cholic acid and chenodeoxycholic acid, respectively. The effect of enzyme concentration on the reaction velocity showed a constant increase in the enzyme activity with increase in enzyme-protein concentration. 7α-HSDH was activated by Na+, K+, Ca2+, and Mn2+ ions and by reducing agents having a thiol group (dithiothreitol, 2-mercaptoethanol). Co2+, Hg2+, Fe3+, Mg2+, Zn2+, Ba2+, and Cu2+ ions, chelating agents (potassium oxalate, heparin, EDTA), oxidizing agents (sodium perchlorate, sodium periodate, sodium persulphate), and detergents (Tween 20, Tween 40, Tween 80, Triton X-100, sodium lauryl sulphate) were inhibitory to 7α-HSDH activity.Key words: 7α-hydroxysteroid dehydrogenase, bile acids, NAD+, Escherichia coli 080, enzyme kinetics.

scholarly journals Antagonistic Effects of Lipids Against the Anti-Escherichia coli and Anti-Salmonella Activity of Thymol and Thymol-β-d-Glucopyranoside in Porcine Gut and Fecal Cultures In Vitro

2021 ◽  
Vol 8 ◽  
Author(s):  
Robin C. Anderson ◽  
Gizem Levent ◽  
Branko T. Petrujkić ◽  
Roger B. Harvey ◽  
Michael E. Hume ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Gastrointestinal Tract ◽  
Vegetable Oil ◽  
Tween 80 ◽  
Bactericidal Effect ◽  
Antagonistic Effect ◽  
Tween 20 ◽  
Production Environment

Strategies are sought to reduce the carriage and dissemination of zoonotic pathogens and antimicrobial-resistant microbes within food-producing animals and their production environment. Thymol (an essential oil) is a potent bactericide in vitro but in vivo efficacy has been inconsistent, largely due to its lipophilicity and absorption, which limits its passage and subsequent availability in the distal gastrointestinal tract. Conjugation of thymol to glucose to form thymol-β-d-glucopyranoside can decrease its absorption, but in vivo passage of effective concentrations to the lower gut remains suboptimal. Considering that contemporary swine diets often contain 5% or more added fat (to increase caloric density and reduce dustiness), we hypothesized that there may be sufficient residual fat in the distal intestinal tract to sequester free or conjugated thymol, thereby limiting the availability and subsequent effectiveness of this biocide. In support of this hypothesis, the anti-Salmonella Typhimurium effects of 6 mM free or conjugated thymol, expressed as log10-fold reductions of colony-forming units (CFU) ml−1, were diminished 90 and 58%, respectively, following 24-h in vitro anaerobic fecal incubation (at 39°C) with 3% added vegetable oil compared to reductions achieved during culture without added oil (6.1 log10 CFU ml−1). The antagonistic effect of vegetable oil and the bactericidal effect of free and conjugated thymol against Escherichia coli K88 tested similarly were diminished 86 and 84%, respectively, compared to reductions achieved in cultures incubated without added vegetable oil (5.7 log10 CFU ml−1). Inclusion of taurine (8 mg/ml), bile acids (0.6 mg/ml), or emulsifiers such as polyoxyethylene-40 stearate (0.2%), Tween 20, or Tween 80 (each at 1%) in the in vitro incubations had little effect on vegetable oil-caused inhibition of free or conjugated thymol. Based on these results, it seems reasonable to suspect that undigested lipid in the distal gut may limit the effectiveness of free or conjugated thymol. Accordingly, additional research is warranted to learn how to overcome obstacles diminishing bactericidal activity of free and conjugated thymol in the lower gastrointestinal tract of food-producing animals.

Kinetic properties of rrn promoters in Escherichia coli

Biochimie ◽  
2002 ◽  
Vol 84 (10) ◽  
pp. 981-996 ◽  
Author(s):  
X Zhang ◽  
P Dennis ◽  
M Ehrenberg ◽  
H Bremer
Keyword(s):  
Escherichia Coli ◽  
Kinetic Properties

pH dependence of the kinetic properties of allosteric phosphofructokinase from Escherichia coli

Biochemistry ◽  
1991 ◽  
Vol 30 (23) ◽  
pp. 5750-5754 ◽  
Author(s):  
Dominique Deville-Bonne ◽  
Florence Bourgain ◽  
Jean Renaud Garel
Keyword(s):  
Escherichia Coli ◽  
Ph Dependence ◽  
Kinetic Properties

scholarly journals FORMULATION AND CHARACTERIZATION OF LAFUTIDINE NANOSUSPENSION FOR ORAL DRUG DELIVERY SYSTEM

2018 ◽  
Vol 10 (2) ◽  
pp. 20 ◽  
Author(s):  
Noor Mohammed Dawood ◽  
Shaimaa Nazar Abdal-hammid ◽  
Ahmed Abbas Hussien
Keyword(s):  
Particle Size ◽  
Fourier Transforms ◽  
Oral Drug Delivery ◽  
In Vitro Release ◽  
Tween 80 ◽  
Precipitation Method ◽  
Oral Drug ◽  
Tween 20 ◽  
Dissolution Profile ◽  
Particle Size Reduction

Objective: The objective of this study was to prepare nanosuspension of a practical water insoluble antiulcer drug which is lafutidine to enhance the solubility, dissolution rate with studying the effect of different formulation variables to obtain the best formula with appropriate physical properties and higher dissolution rate.Methods: Nanosuspension of lafutidine was prepared using solvent anti-solvent precipitation method using Polyvinylpyrrolidone K-90(PVP K-90) as the stabilizer. Ten formulations were prepared to show the effect of different variables in which two formulations showed the effect of stabilizer type, three formulations showed the effect of stabilizer concentration, two formulations showed the effect of combination of polymer with surfactant such as tween 80, three formulations show the effect of stirring speed and three formulations prepare to show the effect of addition of co-surfactant such as tween 20. All these formulations are evaluated for their particle size and entrapment efficiency and in vitro release. The selected one was evaluated for zeta potential, scanning electron microscope, atomic force microscopy, Fourier transforms infrared spectroscopy, differential scanning calorimetry, saturation solubility and stability study.Results: The formulations (F3-F10) were in the nano size. The optimum concentration of the stabilizer was in the formulation when the drug: polymer: surfactant ratio 1:4:4 and the optimum stirring speed was 1500 rpm. Dramatic effect on the particle size reduction was found by the addition of co-surfactant (tween 20) in formulation F7 that has a particle size 15.89±1.8 nm. The selected formula F7 showed an enhanced dissolution profile (10 min) compared to the pure drug at all-time intervals.Conclusion: The results show that the formulation that contains drug: PVP-K90: tween 80: tween 20 in ratio 1:4:2:2 is the best one and can be utilized to formulate lafutidine nanosuspension. 

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