Generation of Reactive Oxygen Species by Menadione

Menadione a soluble form of vitamin K is often used as a generator of reactive oxygen species (ROS such as hydrogen peroxide in cultured cells or microorganisms. In this paper we describe the menadione‑mediated produc‑ tion of superoxide anion in permeabilized yeast. Menadione inactivated aconitase which is the most sensitive enzyme to ROS in the presence of KCN an inhibitor of superoxide dismutase suggesting that menadione can pro‑ duce superoxide as a principal product. Addition of reducing agent including dithiol or NADPH increased aconitase inactivation indicating that the enhanced ROS generation depends on the enzymatic reduction of menadione. Menadione further produced 8‑hydroxy‑2'‑deoxyguanosine in DNA in the presence of copper suggesting menadione/copper‑dependent formation of hydroxyl radical. Menadione may form semiquinone radical by the reac‑ tion with protein thiol residue or nucleic acid under the conditions without enzymatic reduction followed by the for‑ mation of superoxide and further hydroxyl radical in the presence of transition metals causing DNA base damage.