Enzyme group belonging to the enzyme family of oxyreductases (see below enzymes) which act as catalysts for selective oxidations. Oxygenases often contain iron, sometimes also copper. Usually hydroxy groups (-OH) are introduced, but the formation of double bonds or rearrangements can also occur. In addition to the actual substrate, oxygen and alpha-ketoglutarate (αKG) are required for catalysis, whereby CO2 is oxidatively split off from the latter. An important oxygenase is cyclooxygenase, which catalyses the formation of cyclic endoperoxides from unsaturated fatty acids.