Menadione (vitamin K₃), used as a nutritional supplement, is an inhibitor of mitochondrial DNA polymerase γ (pol γ), with an IC 50 value of 6 µM [1].

Pol γ is responsible for all aspects of mitochondrial DNA synthesis, including all replication, recombination of the mitochondrial genome, and repair of mitochondrial DNA damage [1].

In the extract of mitochondrion fraction from HCT116 (p53^+/+ and p53^–/–) cells, menadione at 30 μM inhibited pol γ by more than 80%. In HCT116 cells, 30 μM menadione also caused impairment of mitochondrial DNA replication and repair, and triggered a significant increase in reactive oxygen species (ROS), leading to apoptosis. At a lower concentration of 3 μM, menadione did not significantly increase the ROS level, but was able to effectively inhibit cancer cell proliferation, which could be reversed by supplementing glycolytic substrates [2].

In Emory mice, menadione at a low non-toxic dose of 0.12% (w/w), used as a dietary supplement for 10 to 12 weeks, caused early signs of cataract, such as prominent anterior suture, in 68% of the Emory mice [3].

References:

[1]. Mizushina Y, Yonezawa Y, Yoshida H. Selective inhibition of animal DNA polymerases by fat-soluble vitamins A, D, E and K and their related compounds. Current Enzyme Inhibition, 2007, 3(1): -.

[2]. Sasaki R, Suzuki Y, Yonezawa Y, et al. DNA polymerase gamma inhibition by vitamin K3 induces mitochondria-mediated cytotoxicity in human cancer cells. Cancer Science, 2008, 99(5): 1040-1048.

[3]. Bhuyan D K, Huang X, Kuriakose G, et al. Menadione-induced oxidative stress accelerates onset of Emory mouse cataract in vivo. Current eye research, 1997.