Differential excision from DNA of the C-8 deoxyguanosine reaction products of N-hydroxy-2-aminofluorene and N-acetoxy-N-acetyl-2-aminofluorene by endonuclease S1 from Aspergillus oryzae.

Calf thymus DNA was modified in vitro with [G-3H]N-hydroxy-2-aminofluorene and [G-3H]N-acetoxy-N-acetyl-2-aminofluorene and the nuclease S1 digestion was studied under identical conditions. The ratios of the maximum reaction rate (V) and the Michaelis constant (Km), V/Km, indicate that 2-aminofluorene(AF)-modified DNA is hydrolyzed 3 times more slowly than N-acetyl-2-aminofluorene(AAF)-modified DNA under similar reaction conditions. The AF-modified DNA was slightly more susceptible to partial digestion by nuclease S1 than unmodified control DNA. These results suggest that the local regions of denaturation induced by AF substitution are smaller than those associated with AAF modification.