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Abstract
1. Arylamines such as 2-aminofluorene (2-AF) are known teratogens and transplacental carcinogens in laboratory animal species. Although exposure of women to arylamines is likely to occur during pregnancy, how these chemicals are metabolized by the enzymes from the human conceptual tissues is currently unknown.
2. Highly purified preparations of peroxidase isolated from human intrauterine conceptual tissues at 8 weeks of gestation were used to study in vitro metabolism of 2-AF. The oxidation of 2-AF was examined spectrophotometrically whereas the bioactivation was assessed from the covalent binding to protein and DNA using [3H] 2-AF.
3. Using guaiacol as a model substrate, the purified preparations of peroxidase used exhibited a specific activity of 15–20 μmol/min/mg protein. 2-AF oxidation was found to be enzymatic in nature. Kinetic data obtained under optimal assay conditions yielded a Km = 41 μM for 2-AF, 8.33 μM for H2O2, and a Vmax = 1.2 μmol 2-AF oxidized/min/mg protein.
4. Under optimal assay conditions, the covalent binding of reactive intermediate(s) to protein and DNA (nmol equivalent/min/mg enzyme/mg bovine serum albumin or calf thymus DNA) was observed at the rate of about 3.75 ± 0.39 and 1.90 ± 0.11 respectively.
5. A significant decline in the rate of both oxidation and bioactivation of 2-AF was observed in the presence of classical peroxidase inhibitors, KCN and NaN3.