To measure the peroxidase substrates in the presence of phenol and 4-aminoantipyrine Worthington book value of Epsilon is 6.58 was reported . But I read somewhere else that is not a constant number and the number of Epsilon is = Kcat/Km. I'm confused.
(Measurement of peroxidase activity in the presence of substrates 4-aminoantipyrine and phenol)
Please advise me.
Hi there,
Epsilon has nothing to do with kcat / Km. The former is the specific factor for an absorbing molecule making the link between the measured absorbance at a given wavelength and the actual concentration of this compound in the sample. This is the Beer'law: Absorbance = Epsilon*l*concentration.
kcat / Km is the catalytic efficiency characterizing the activity of a given enzyme toward a given substrate. This is a constant as it is a combination of specific rate constants.
In the peroxydase assay you mentioned the epsilon of 6.58 is the one used to convert directly the observed variation of absorbance at 510nm per minute into an activity expressed in unit/mg (one unit being defined as 1 µM of hydrogen peroxyde consumed per minute). It is specific of the system used (reaction of H2O2 with a spcific substrate to generate a specific absorbing molecule) during the assay and constant.
Dear Dominique Liger
Thank you very much for your answer.
So how do the calculations in various articles Epsilon to measure peroxidase number to each a numerical report.
Epsilon how to calculate their number?
Thanks for the guide.
Dear Dominique Liger
I apologize for wrong questions. In any case, thank you for guide.
Cordially yours Sepideh
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