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Chance1952_Catalase_Mechanism

ABSTRACT: This model is described in the article: The mechanism of catalase action. II. Electric analog computer studies. Britton Chance, David S Greenstein, Joseph Higgins, CC Yang, Arch Biochem. 1952 37:322-39. PubmedID:14953444 Summary: An electric analog computer has been constructed for a study of the kinetics of catalase action. This computer gives results for the formation and disappearance of the catalase-hydrogen peroxide complex that are in good agreement with the experimental data. The computer study verifies an approximate method for the computation of the velocity constant for the combination of hydrogen peroxide and catalase and justifies the simple formula used previously to compute the velocity constant for the reaction of the catalase-hydrogen peroxide complex with donor molecules. Finally, the computer data show that the binding of peroxide to catalase is a practically irreversible reaction. The reaction of the enzyme-substrate complex, p, with the electron donor, a, is bimolecular, although in the article, as a is assumed to be constant, it is modelled using an apparent rate constant consisting of the product of the rate constant, k4, and the concentration of a. In this implementation, the concentration of a is set to 1 and the value of k4 just adapted so that the product equals the values given for k4*a in the article. The specific parameter values are taken from Fig 3. The graphs do not exactly match those in the paper, this may be due to the different simulators used.

SUBMITTER: Kieran Smallbone

PROVIDER: BIOMD0000000282 | BioModels | 2010-10-10

REPOSITORIES: BioModels

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The mechanism of catalase action. II. Electric analog computer studies.

CHANCE B B GREENSTEIN D S DS HIGGINS J J YANG C C CC

Archives of biochemistry and biophysics 19520601 2

PMID: 14953444

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Project description:Default parameter values are those in the right hand panel of Fig 12. The other panels may be obtained by setting X to 1, 2 or 4, and K3 to 0, 1/2 or 1. This model is described in: The kinetics of the enzyme-substrate compound of peroxidase. Britton Chance, Journal of Biological Chemistry, 151, 553-577, 1943. PDF at JBC reprinted in: Adv Enzymol Relat Areas Mol Biol. 1999;73:3-23. PubmedID:10218104> Abstract: Under the narrow range of experimental conditions, and at a temperature of approximately 25 degrees, the following data were obtained. 1. The equilibrium constant of peroxidase and hydrogen peroxide has a minimum value of 2 x 10(-8). 2. The velocity constant for the formation of peroxidase-H2O2 Complex I is 1.2 x 10(7) liter mole-1 sec.-1, +/- 0.4 x 10(7). 3. The velocity constant for the reversible breakdown of peroxidase-H2O2 Complex I is a negligible factor in the enzyme-substrate kinetics and is calculated to be less than 0.2 sec.-1. 4. The velocity constant, k3, for the enzymatic breakdown of peroxidase-H2O2 Complex I varies from nearly zero to higher than 5 sec.-1, depending upon the acceptor and its concentration. The quotient of k3 and the leucomalachite green concentration is 3.0 x 10(4) liter mole-1 sec.-1. For ascorbic acid this has a value of 1.8 x 10(5) liter mole-1 sec.-1. 5. For a particular acceptor concentration, k3 is determined solely from the enzyme-substrate kinetics and is found to be 4.2 sec.-1. 6. For the same conditions, k3 is determined from a simple relationship derived from mathematical solutions of the Michaelis theory and is found to be 5.2 sec.-1. 7. For the same conditions, k3 is determined from the over-all enzyme action and is found to be 5.1 sec.-1. 8. The Michaelis constant determined from kinetic data alone is found to be 0.44 x 10(-6). 9. The Michaelis constant determined from steady state measurements is found to be 0.41 x 10(-6). 10. The Michaelis constant determined from measurement of the overall enzyme reaction is found to be 0.50 x 10(-6). 11. The kinetics of the enzyme-substrate compound closely agree with mathematical solutions of an extension of the Michaelis theory obtained for experimental values of concentrations and reaction velocity constants. 12. The adequacy of the criteria by which experiment and theory were correlated has been examined critically and the mathematical solutions have been found to be sensitive to variations in the experimental conditions. 13. The critical features of the enzyme-substrate kinetics are Pmax, and curve shape, rather than t1/2. t1/2 serves as a simple measure of dx/dt. 14. A second order combination of enzyme and substrate to form the enzyme-substrate compound, followed by a first order breakdown of the compound, describes the activity of peroxidase for a particular acceptor concentration. 15. The kinetic data indicate a bimolecular combination of acceptor and enzyme-substrate compound. This model is the one described in the appendix of the article. It reproduces, amongst others, figure 12. The parameters and concentrations used are rescaled as stated in the article. K2 and K3 stand for k2 and k3, respectively, divided by k1.

Dataset Information

Chance1952_Catalase_Mechanism

Publications

The mechanism of catalase action. II. Electric analog computer studies.

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