Function of cupric ion in the breakage of pBR322 ccc-DNA by D-glucosamine

The function of Cu2+ in the breakage of pBR322 ccc-DNA by d-glucosamine was investigated using agarose gel electrophoresis. The maximal stimulatory effects on the DNA breakage and ·OH production were observed at the same concentration of Cu2+ in an aqueous solution of d-glucosamine. An aqueous solution of d-glucosamine containing 1 mm of Cu2+ generated less O2− and H2O2 than ·OH. The generation of these active oxygens, either in the presence or absence of Cu2+, was affected little by the addition of DNA. Superoxide dismutase inhibited the DNA-breaking action of d-glucosamine in the absence, but not the presence, of Cu2+. Hydroxyl radical-scavengers inhibited the reaction in the presence as well as the absence of Cu2+. The reaction in the presence of Cu2+ was inhibited by d-GMP and a different kind of DNA. An atomic absorption analysis showed that copper binding to pBR322 ccc-DNA was concentration-dependent. Cupric ions were found to bind to the ccc-DNA, and were found to stimulate the autoxidation of d-gl...