that allows for the binding of NADPH, and studies show that if it is removed, it is depleted, catalytic activity increases. Mechanism The mechanism of the flavin reductase process is described above and most likely follows the ping pong kinetic pattern. This means that it is a bisubstrate-biproduct mechanism. First the flavin reductase enzyme binds NADPH and stabilizes the release of the hydride. Because of sterics, it is not possible for the enzyme to bind both NADPH and the flavin. For this reason, NADP+ is released and then the flavin substrate is bound to the enzyme. In this step, the hydride attacks Nitrogen on the flavin, which allows for another protonation. Then, reduced flavin is released from flavin reductase as the second product. In this way, the reduction of flavin is dependent on flavin reductase binding first to NADPH, or in some cases NADH. Biological function Flavin reductases exist in a variety of organisms, including animals and bacteria. In luminous organisms, flavin reductase is important in the luciferase process. In an experiment with P. fischeri and B. harveyi cells, bioluminescence was increased as the in vivo concentration of flavin reductase was increased. This suggests a connection between either a flavin reductase-luciferase complex or reduced flavin and the luminescence process in bacteria. The bacteria oxidize the reduced flavin mononucleotide to oxidized FMN and transfer it through free fusion to generate light. In humans, flavin reductase often catalyzes an NADPH dependent reduction of flavin mononucleotide which occurs in methemoglobin in erythrocytes and the liver. It has also been suggested that flavin reductases play a role in the production of hydrogen peroxide. This would be biologically helpful as H2O2 assists the body in maintaining homeostatic microbiota. A study showed that women with lactobacillus that produced hydrogen peroxide were less likely to develop bacterial vaginosis prebirth. It was also seen in Trichomonas vaginalis that decreased levels of flavin reductase increased the cycling of metronidazole because flavin reductase has an antioxidative effect, which decreases oxygen levels, maintaining the metronidazole population. Future of the enzyme Currently, it is seen that bacterial flavin reductase can be used to sensitize carcinomas, or tumors to pro drugs. At first, flavin reductases were used to target the hypoxia of tumors. However, current research is showing an interest in these reductase molecules, specifically, MSuE from Pseudomonas aeruginosa which has been shown to increase the effectiveness of the prodrugs for cancerous tumors.