Peroxidase-catalysed binding of [U-¹⁴C]phenol to DNA

Abstract

1. ¹⁴C-Phenol binds irreversibly to calf-thymus DNA in the presence of horseradish peroxidase and hydrogen peroxide, approximately 65% of the added phenol was bound to DNA. Binding was maximal at an equimolar concentration of hydrogen peroxide. Binding also occurred to homopolyribonucleotides polyadenylic acid, polyguanylic acid, polycytidylic acid and polyuridylic acid, and suggests that binding is relatively non-specific with respect to the nucleotide bases.

2. p,p'-Biphenol, p,p'-biphenoquinone, o,o'-biphenol and two unidentified products were formed by the oxidation of phenol, in the presence and in absence of DNA. DNA accelerated phenol oxidation four fold and prevented the polymerization of oxidized phenol products, but was found to have no effect on the range of ethyl acetate-extractable products. Phenol accelerated the metabolism of o,o'-biphenol but had no effect on p,p'-biphenol metabolism. The mechanism of phenol activation is not clear, but p,p'-biphenoquinone binds to protein and not to DNA.

3. DNA binding was prevented by glutathione, N-acetyl-cysteine and ascorbate, and the mechanism was shown to involve reduction of the activated phenol intermediates and the formation of conjugates with glutathione and N-acetyl-cysteine. DNA binding was not inhibited by lysine and proline.