Horseradish Peroxidase Reaction

Oxidation of ABTS using Horseradish Peroxidase (EC 1.11.1.7)

Chemical Equation

$${Hydrogen}\ {Peroxide} + {ABTS} \rightleftharpoons {ABTS}_{Oxidised} + {Water}$$

Rate Equation

$$\nu = \frac{K_{cat}[HRP] \frac{[H_2 O_2]}{K_{m,H_2 O_2}}\left({ 1- \frac{[H_2 O_2][ABTS]}{[ABTS_{Oxidised}]} \frac{1}{K_{eq}}} \right)}{1+\frac{[H_2 O_2]}{K_{m,H_2 O_2}}+\frac{[ABTS]}{K_{m,ABTS}}+\frac{[H_2 O_2][ABTS]}{K_{m,ABTS}K_{m,H_2 O_2}}+\frac{[ABTS_{Oxidised}]}{K_{m,ABTS_{Oxidised}}}} $$

where:

Symbol	Meaning
$$K_{m,A}$$	Michaelis constant of species A
$$K_{cat}$$	Turnover number
$$[A]$$	Concentration of A
$$ \nu$$	Reaction Rate

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Parameter Sourcing

Kcat and Km parameters were collected from BRENDA

Keq was calculated using the Van’t Hoff equation using the Gibbs free energy sourced from MetaCyc

$$ K_{eq} = e^{\frac{-\Delta G} {RT}}$$
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Parameters with uncertainty

Km

Uncertainty in Km is introduced through the range of experimental parameters sourced. Properties of the raw data can be seen in the table below:

Property	Value
Minimum	0.005 mM
Maximum	23.3 mM
Mean	1.78 mM
Parameters Sourced	50

Kcat

Uncertainty in Kcat is introduced through the range of experimental parameters sourced. Properties of the raw data can be seen in the table below:

Property	Value
Minimum	0.3 s-1
Maximum	201.8 s-1
Mean	59.4 s-1
Parameters Sourced	5

Keq

Uncertainty in Keq is introduced using a uniform range of temperature variations (298 K ± 5 K). Properties of this can be seen in the table below:

Property	Value
$$-\Delta G$$	254.520071288 kJ
Minimum Temperature	293 K
Maximum Temperature	303 K

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