Enzymatic Activation of DNA Cleavage by Dynemicin A and Synthetic Analogs

Abstract

Dynemicin A (1), a member of the enediyne family of natural products, binds to double-stranded DNA (K_B ∼ 10^4 M^(-1)) and in the presence of millimolar concentrations of a reducing cofactor such as NADPH or GSH reacts to cleave DNA. In this work, we show that the two flavin-based enzymes ferredoxin−NADP^+ reductase and xanthine oxidase catalyze the reductive activation of 1 by NADPH and NADH, respectively. The enzyme-catalyzed reductive activation of 1 leads to more rapid and efficient cleavage of DNA, even with 10−20-fold lower concentrations of the stoichiometric reductant. Significantly, the enzymatic systems are also found to activate the tight-binding (K_B ≥ 10^6 M^(-1)) synthetic dynemicin analogs 3 and 5 toward DNA cleavage. These same analogs do not undergo reductive activation with NADPH or NADH alone, where evidence has been obtained to support the proposal that the DNA-bound drugs are protected from reductive activation. The new enzymatic activation processes described may have important implications for chemistry occurring with 1 and synthetic analogs in vivo, as well as for the future development of dynemicin-based anticancer agents.

Additional details