Oxidative metabolism of propylthiouracil by peroxidases from rat bone marrow

Abstract

1.Propylthiouracil (PTU) was degraded by myeloperoxidase (MPO) or eosinophil peroxidase (EPO), purified from rat bone marrow, in the presence of H₂O₂ and Cl⁻. In the absence of either H₂O₂ or Cl⁻, MPO and EPO do not degrade PTU. Optimum concentrations of KCl for MPO and EPO were 50 and 250 mM, respectively.

2.The characteristics of PTU degradation by MPO-H₂O₂-Cl⁻ were similar to those of the chlorinating activity of the peroxidase.

3.Hypochlorous acid as well as MPO-H₂O₂-Cl⁻ also degraded PTU. Metabolites of PTU degradation by MPO-H₂O₂-Cl⁻, which were separated by C₁₈ reversed phase h.p.l.c., were the same as those produced by hypochlorous acid.

4.Of the metabolites of PTU formed by MPO-H₂O₂-Cl⁻, one was identified as PTU sulphonic acid (6-propyl-4-hydroxypyrimidine-2-sulphonate) and another seemed to be propyluracil.