ROS generated in redox cycling contributes to anticancer activity of vitamin K . NQO1 competes with enzymes that redox cycle vitamin K to formation of semiquinone and ROS . NQO1is therefore able to detoxify vitamin K3 and protect cells against oxidative stress.
It has been argued that a water molecule ( HOH39 ) arrives at the active site and is coordinated by His207 of subunit B, Arg31 of subunit C, and Asp82 of subunit D . The semiquinone species is protonated by protons delivered from HOH39, completing the ubiquinone reduction to ubiquinol.
