An algebraic model for the kinetics of covalent enzyme inhibition at low substrate concentrations

2015 ◽  
Vol 484 ◽  
pp. 82-90 ◽  
Author(s):  
Petr Kuzmič ◽  
James Solowiej ◽  
Brion W. Murray
Keyword(s):  
Enzyme Inhibition ◽  
Algebraic Model ◽  
Kinetics Of ◽  
Substrate Concentrations

scholarly journals Kinetics of Enzymatic Hydrolysis of Southeast Sulawesi Sago Starch

2020 ◽  
pp. 53-61
Author(s):  
Ansharullah Ansharullah ◽  
Muhammad Natsir
Keyword(s):  
Enzymatic Hydrolysis ◽  
Maximum Velocity ◽  
Enzyme Concentration ◽  
Hydrolysis Rate ◽  
Sago Starch ◽  
Optimum Conditions ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations ◽  
Menten Constant

The aims of this study were to characterize the kinetics of enzymatic hydrolysis of sago starch, obtained from Southeast Sulawesi Indonesia. The enzyme used for hydrolysis was bacterial ∝-amylase (Termamyl 120L from Bacillus licheniformis, E. C. 3.2.1.1).  The method to determine the initial velocity (Vo) of the hydrolysis was developed by differentiation a nonlinear equation (NLE).  The Vo of the hydrolysis was measured at various pH (6.0, 6.5,and 7.0), temperatures (40, 60, 75 and 95oC), enzyme concentrations (0.5, 1.0, 1.5 and 2.0 µg per mL) and in the presence of 70 ppm Ca++. The optimum conditions of this experiment were found to be at pH 6.5 – 7.0 and 75oC, and the Vo increased with increasing enzyme concentration. The Vo values at various substrate concentrations were also determined, which were then used to calculate the enzymes kinetics constant of the hydrolysis, including Michaelis-Menten constant (Km) and maximum velocity (Vmax) using a Hanes plot.  Km and Vmax values were found to be higher in the measurement at pH 7.0 and 75oC. The Km values  at four  different combinations of pH and temperatures (pH 6.5, 40oC; pH 6.5, 75oC; pH 7.0, 40oC; pH 7.0, 75oC) were found to be 0.86, 3.23, 0.77 and 3.83 mg/mL, respectively; and Vmax values were 17.5, 54.3, 20.3 and 57.1 µg/mL/min, respectively. The results obtained showed that hydrolysis rate of this starch was somewhat low.

Longan seed polyphenols inhibit α-amylase activity and reduce postprandial glycemic response in mice

2021 ◽  
Author(s):  
Ting He ◽  
lei zhao ◽  
Yan Chen ◽  
Xin Zhang ◽  
Zhuoyan Hu ◽  
...  
Keyword(s):  
Enzyme Inhibition ◽  
Amylase Activity ◽  
Glycemic Response ◽  
Inhibition Assay ◽  
Inhibition Kinetics ◽  
Enzyme Inhibition Kinetics ◽  
Longan Seed ◽  
Kinetics Of

The effects of longan seed polyphenols (LSPs) on postprandial glycemic response in mice were investigated, enzyme inhibition kinetics of LSPs against α-amylase were studied using an inhibition assay in vitro,...

KINETIC STUDIES ON THE HYDROLYSIS OF BENZOYLCHOLINE BY HUMAN SERUM CHOLINESTERASE

1956 ◽  
Vol 34 (1) ◽  
pp. 637-653 ◽  
Author(s):  
W. Kalow ◽  
K. Genest ◽  
N. Staron
Keyword(s):  
Kinetic Studies ◽  
Reaction Rates ◽  
Serum Cholinesterase ◽  
Initial Reaction ◽  
Ultraviolet Spectrophotometry ◽  
First Order ◽  
Low Concentrations ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations

Benzoylcholine stands out from other known substrates of serum cholinesterase because of its high apparent affinity for this enzyme combined with a rapid rate of destruction. The reaction kinetics of the hydrolysis of benzoylcholine can be studied by ultraviolet spectrophotometry, since the absorbance decreases in proportion to the concentration of substrate. Kinetic data obtained by measuring initial reaction rates, and by analyzing continuous hydrolysis curves, are the same within the range of experimental error. The enzymatic data are compatible with the assumption that in the presence of high substrate concentrations a complex consisting of esterase and two substrate molecules is formed. This complex is hydrolyzed more slowly than the complex containing one molecule of substrate which is formed at low concentrations of benzoylcholine. Alkaline hydrolysis of benzoylcholine follows the kinetics of a first order reaction.

scholarly journals Kinetics of irreversible enzyme inhibition by an unstable inhibitor

1974 ◽  
Vol 141 (2) ◽  
pp. 601-603 ◽  
Author(s):  
Emmanuel T. Rakitzis
Keyword(s):  
Methyl Ester ◽  
Enzyme Inhibition ◽  
Cathepsin D ◽  
Fluorescein Isothiocyanate ◽  
Order Reaction ◽  
Enzyme Inactivation ◽  
First Order Reaction ◽  
Mathematical Treatment ◽  
First Order ◽  
Kinetics Of

A mathematical treatment for the general case of enzyme inactivation by an inhibitor that breaks down in solution in a first-order reaction is presented. Cathepsin D was inactivated by fluorescein isothiocyanate with a Ki of 4.47μm. Kinetic constants were also determined for the inactivation of cathepsin D by 1,1-bis(diazoacetyl)-2-phenylethane, and the inactivation of pepsin C by diazoacetyl-dl-norleucine methyl ester.

Kinetics of rat liver GM2 ganglioside-β-D-N-acetylhexosaminidase

1980 ◽  
Vol 58 (1) ◽  
pp. 82-88 ◽  
Author(s):  
Anton Novak ◽  
J. Alexander Lowden
Keyword(s):  
Electrical Conductivity ◽  
Critical Micelle Concentration ◽  
Rat Liver ◽  
Specific Activity ◽  
Sodium Taurocholate ◽  
Gm2 Ganglioside ◽  
Spectral Shifts ◽  
Kinetic Plots ◽  
Kinetics Of ◽  
Substrate Concentrations

The kinetics of β-D-N-acetylhexosaminidase against GM2 ganglioside were examined. We used a crude preparation of rat liver as the enzyme source because purification of β-D-N-acetylhexosaminidase results in a decrease in specific activity against GM2 ganglioside. Kinetic plots were not linear but showed a break. At substrate concentrations less than 50 μM the Vmax was 6 pmol GM2 hydrolyzed per hour per micromole 4-MU-GlcNAc hydrolyzed per hour (pmol GM2/μmol 4-MU-GlcNAc) and the Km was 5 μM. At substrate concentrations greater than 50 μM, the Vmax was 7 pmol GM2/μmol 4-MU-GlcNAc and the Km was 14 μM. The critical micelle concentration of GM2 ganglioside was 20–25 μM as determined by spectral shifts of the dye pinacyanol chloride in association with GM2, and 10–15 μM from electrical conductivity measurements which also showed the end of the monomer–micelle transition to occur at 40–50 μM GM2. The increasing excess of micellar substrate at greater than 50 μM GM2 explains the discontinuity in the kinetic plots. Sodium taurocholate had a critical micelle concentration of 9–11 mM using pinacyanol chloride and 2.5–3 mM using electrical conductivity. When included in the assay mixture at a concentration of 10 mM, sodium taurocholate produced a linear kinetic plot. This is probably due to the formation of mixed micelles of detergent and GM2 ganglioside. The Vmax was 200 pmol GM2/μmol 4-MU-GlcNAc and the Km was 93 μM. The data suggest that ganglioside hydrolysis occurs more readily when the substrate is incorporated into a membrane-like environment.

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