Uric acid inhibits L-DOPA-CU(II) mediated DNA cleavage.

It has been proposed that considerable DNA damage may be caused by endogenous metabolites produced during the body's normal metabolic processes. We have previously shown that L-DOPA, in the presence of Cu(II) leads to oxidative DNA breakage in vitro. Uric acid is considered to be a naturally occuring antioxidant and is present in plasma at a relatively high concentration. In this paper we report that uric acid inhibits L-DOPA-Cu(II) mediated DNA cleavage at concentrations similar to or lower than those found in plasma. Xanthine, which is the structural analogue of uric acid is a more potent inhibitor of the reaction. Uric acid was also shown to directly quench the generation of hydroxyl radicals by L-DOPA-Cu(II). The results have been discussed in relation to the putative protective role of uric acid against endogenous DNA damage by oxygen radicals.