Enhancement of the catalytic inhibition of topo II by hydroquinone; 4,4′-biphenol; and catechol following peroxidase activation.

The pBR322 plasmid DNA (300 ng) was combined with topo II (6 U) following a 10-minute incubation with activated compound (1, 10, 30, 100, 300 μM) in the absence or presence of 100 μM etoposide. (A) DNA cleavage assay performed with peroxidase-activated hydroquinone. (B) DNA cleavage assay performed with peroxidase-activated 4,4′-biphenol. (C) DNA cleavage assay performed with peroxidase-activated catechol. All samples, including untreated controls, contain identical concentrations of activating agents. Reactions were interpreted as described in Figure 1.