Menaquinone 9 is a form of vitamin K2 which acts as a prothrombogenic agent. Studies suggest that menaquinones are susceptible to rapid photooxidation at the isoprene unit closest to the quinone ring in the presence of oxygen and light. In addition, Menaquinone 9 is a functional electron transfer component in nitrate reductase. Menaquinone 9 can be detected in samples via UV spectroscopy at 248 nm. It is known that menaquinones act as intermediates accepting 2 electrons from each NADH molecule and transferring them to other molecules for anaerobic respiration in bacteria. Addditionally, vitamin K can be reduced by the enzyme vitamin K epoxide reductase.