Alteration of Activation Energy of a Reaction in the Catalase of Human Erythrocyte by Cimetidine, an In vitro Thermokinetic Study

Author(s):

Dariush Minai-Tehrani*   Pages 148 - 151 ( 4 )

Abstract:

Background: Hydrogen peroxide is normally formed during the metabolic pathway of the body. It is a toxic compound for vital cells, which can oxidize many macromolecules and cause damage in cells. Catalase can degrade H₂O₂ in cells and prevent cell injury. Cimetidine is a histamine H₂ receptor blocker which decreases the release of stomach acid and is used for gastrointestinal diseases. Cimetidine inhibited catalase by mixed inhibition.

Objective: In this study, the effect of temperature on the binding of cimetidine to human erythrocyte catalase was investigated and kinetic factors of the binding were determined.

Results: Dixon plot confirmed the mixed type of inhibition and determined the Ki of the drug. The maximum activity of the enzyme was observed at 30°C. Arrhenius plot demonstrated that the activation energy of the enzyme reaction in the absence and presence of cimetidine was about 4.7 and 8.13 kJ/mol, respectively. The temperature coefficient (Q₃₀-₄₀) was determined as about 1.11 and 1.09 in the absence and presence of cimetidine.

Conclusion: Cimetidine was able to increase the activation energy of the reaction of catalase, which confirmed the inhibition of the enzyme based on the kinetic results.

Keywords:

Activation energy, enzyme, kinetics, erythrocyte, inhibition, cimetidine.

Affiliation:

BioResearch Lab, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran

Graphical Abstract:

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