The Oxidation of Guaiacol,Serotonin, o-Cresol,p-Cresol,m-Cresol,Homovanillic Acid,and m-Tyrosine by Horseradish Peroxidase and Hydrogen Peroxide

Abstract

A survey of 14 substrates for the fluorometric determination of the oxidative enzyme-horseradish peroxidase was carried out. The compounds which seemed to act well as substrates are serotonin, guaiacol, o-cresol, p-cresol, m-cresol, homovanillic acid and m-tyrosine. L-Epinephrine, equilenin, equilin, β-estradiol, estriol, and estrone were studied and found not to be substrates of the system.

The kinetics of the oxidation reactions were studied. They followed the Michaelis constant rate equation. The Michaelis constant, Km, was determined by a Lineweaver-Burk plot for each substrate.

It would appear that the presence of a group in the ortho, para, or meta position of the phenolic ring decreases the binding of the subtrate to the enzyme's active site, as shown by the km values obtained. It may be concluded that m-tyrosine is the best substrate (lowest km value) when compared to all the substrates which have been studied to date by the authors.