Horseradish peroxidase. XXXII. pH dependence of the oxidation of L-(−)-tyrosine by compound I
- 1 December 1978
- journal article
- research article
- Published by Canadian Science Publishing in Canadian Journal of Biochemistry
- Vol. 56 (12) , 1115-1119
- https://doi.org/10.1139/o78-175
Abstract
The rate of oxidation of L-(-)-tyrosine by horseradish peroxidase (EC 1.11.1.7) compound I was studied as a function of pH at 25.degree. C and ionic strength 0.11. Over the pH range of 3.20-11.23 major effects of 3 ionizations were observed. The pKa values of the phenolic (pKa = 10.10) and amino (pKa = 9.21) dissociations of tyrosine and a single enzyme ionization (pKa = 5.42) were determined from nonlinear least squares analysis of the log rate vs. pH profile. The less acidic form of the enzyme was most reactive: hence, the reaction is described as base catalyzed. The rate of tyrosine oxidation falls rapidly with the deprotonation of the phenolic group.This publication has 7 references indexed in Scilit:
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