In biochemistry, oxidoreductase is a large group of enzymes that are involved in redox reaction in living organisms and in the laboratory. Oxidoreductase enzymes catalyze reaction involving oxygen insertion, hydride transfer, proton extraction, and other essential steps. There are a number of metabolic pathways like glycolysis, Krebs cycle, electron transport chain and oxidative phosphorylation, drug transformation and detoxification in liver, photosynthesis in chloroplast of plants, etc. that require the direct involvements of oxidoreductase enzymes. In addition, degradation of old and unnecessary endogenous biomolecules is catalyzed by a family of oxidoreductase enzymes, e.g., xanthine oxidoreductase. Oxidoreductase enzymes use NAD, FAD, ...