The term oxidoreductase encompasses a group of enzymes that are responsible for the oxidation/reduction of certain substrates by the transfer of electrons from one molecule (the oxidant) to another (the reductant). This can be achieved through the addition of oxygen to the molecule or by the removal of a hydrogen or of one or more electrons. They often use the cofactors NAD+/NADP+ as intermediate electron acceptors during the mechanism process.
Different groups of oxidoreductases are classified by the reactions they carry out. Dehydrogenases describes those enzymes that oxidize a substrate by removing hydrogen, peroxidases catalyze reactions in which the reduction of a peroxide is carried out by a substrate that donates two hydrogens , and an oxygenase directly transfers an oxygen to the substrate. Other classifications include hydrogenases and reductases.
Oxidoreductases play major roles in many of the major metabolic pathways including tricarboxylic acid cycle, pentose phosphate pathway, lipid metabolism, cholesterol metabolism, and photosynthesis just to name a few. During anabolic processes the enzymes use energy to create the metabolite products, while during catabolic processes they can create ATP, an energy source for the organism.
The number of enzymes included in this classification are numerous and we will begin to explore them by looking more in depth to three examples: Glutamate Dehydrogenase, Aldehyde Reductase, and Chloroperoxidase.