The relationship between ionization potential and prostaglandin H synthase-catalyzed binding of aromatic hydrocarbons to DNA

A series of polycyclic aromatic hydrocarbons (PAH) with ionization potentials (IP) ranging from 7.7 to 6.96 eV were examined for their ability to bind to DNA in vitro via the prostaglandin H synthase (PHS)-catalyzed co-oxidation of PAH. A relatively low IP was required for significant binding of PAH to DNA to occur. PAH with IP below ∼7.35 eV were active in the binding reaction, while those with IP at or above 7.35 eV exhibited much lower levels of binding. Among the PAH which bound at high levels, there was no correlation between the extent of binding and IP. The results suggest that the prostaglandin H synthase-mediated binding of PAH to DNA occurs by one-electron oxidation, similarly to previously reported horseradish peroxidase (HRP)-catalyzed binding of PAH to DNA.