The mechanism of myeloperoxidase-catalysed oxidation of aminopyrine
- 1 January 1990
- journal article
- research article
- Published by Taylor & Francis in Xenobiotica
- Vol. 20 (9), 957-965
- https://doi.org/10.3109/00498259009046911
Abstract
1. Myeloperoxidase catalysed the H2O2-supported oxidation of aminopyrine in the presence of Cl-, generating the aminopyrine cation radical (AP+). The rate of AP+ formation was determined by monitoring the absorbance at 565 nm. The pH optimum of the reaction was around 5.0. The rate of AP+ formation increased with increasing concentration of aminopyrine. Inhibition by excess H2O2 was seen at pH 4.5–5.5. 2. When Cl- was replaced by Br-, the rate of AP+ formation increased significantly, and inhibition by H2O2 became less evident and was observed only at pH 5.5. The rate of chemical oxidation of aminopyrine by HOCI was much slower than that by Br2. 3. Compared with the chlorination of monochlorodimedone (MCD), the reaction between aminopyrine and HOCl, produced by the enzymic peroxidation of CI-, is rate limiting in the myeloperoxidase-catalysed oxidation of aminopyrine. The differences in kinetic behaviour between the myeloperoxidase-catalysed chlorination of MCD and oxidation of aminopyrine are explained by the low reactivity of HOCI towards aminopyrine.This publication has 21 references indexed in Scilit:
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