Xenobiotic oxidation during early pregnancy in man: Peroxidase catalysed chemical oxidation in conceptal tissues

Abstract

1. A membrane-bound peroxidase activity was isolated and purified from pooled samples of human intrauterine tissue (embryo, placenta, amnion, chorion and uterine decidua) of 4–6 weeks of gestation.

2. The H₂O₂-dependent guaiacol oxidation catalysed by the purified peroxidase exhibited a specific activity of 10.82 ± 1.81 μmol/min/mg protein.

3. The optimum conditions required for guaiacol oxidation catalysed by the peroxidase included 18mM guaiacol, 400μM H₂O₂, pH9.0, and 2μg/ml enzyme protein. The guaiacol oxidation was inhibited by KCN and NaN₃ with IC₅₀s of 17.6 and 22 μM, respectively.

4. Several other endogenous and exogenous chemicals also underwent H₂O₂-dependent oxidation catalysed by the purified peroxidase. These results suggest that peroxidase may be one of the major pathways of xenobiotic oxidation present in organogenesis-stage human conceptal tissues influencing the toxicity of chemicals to which the developing embryo is exposed.