The kinetics of peroxidase action

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Abstract
Using per-oxidase prepared by the method of Willstatter and Stoll from horseradish, with leucomalachite green as substrate, the effect of varying H2O2 concentrations on the temp. coefficient was investigated over the range of concentrations 6 X 10-8 and 1.3 X 10-6 M. Q10 for the latter concentration was 1.9 between 10 and 20[degree], 1.8 between 20 and 30[degree], in agreement with Willstatter and Weber''s value for a peroxide concentration of 7.4 X 10-4 M., thereby disproving Haldane''s suggestion that at low concentrations of peroxide Q10 would be unity. The effect of varying concentrations of peroxide and reducing substrate (guaicol at pH 4.7) can be explained on Woolf''s theory that enzyme reactions occur only through the combination of enzyme and substrate, since the inhibition with excess peroxide can be removed by either removal of the peroxide by catalase, or addition of reducing substrate. The experimental results can be explained on this hypothesis and on Haldane''s theory that the substrate is capable of combining in 2 ways with the enzyme, one combination being inactive. Either excess peroxide or excess reducing substrate produce inactive compounds.

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