dioxygenasen

Dioxygenases are enzymes that catalyze the incorporation of both atoms of molecular oxygen (O2) into substrates. In contrast to monooxygenases, which insert one oxygen atom into the substrate while reducing the other to water, dioxygenases transfer both oxygen atoms from O2 to the product.

Dioxygenases are structurally and mechanistically diverse and are commonly classified into several families. Non-heme iron(II)-dependent dioxygenases use Fe(II) at the active site to activate O2, often performing hydroxylation or ring cleavage. A prominent subclass is the α-ketoglutarate-dependent dioxygenases, which require α-ketoglutarate as a cosubstrate; αKG is decarboxylated to succinate and CO2 during the reaction while the substrate is oxidized. Rieske non-heme iron dioxygenases contain a Rieske [2Fe-2S] center and a mononuclear iron site and catalyze cis-dihydroxylation of aromatic rings, enabling ring cleavage in pollutant degradation. Intradiol and extradiol dioxygenases are ring-cleaving enzymes that act on catechols: intradiol enzymes cleave between the two hydroxyl groups, while extradiol enzymes cleave adjacent to one hydroxyl group, facilitating breakdown of aromatic compounds. Heme-containing dioxygenases, such as cyclooxygenases, insert two oxygen atoms into unsaturated substrates and participate in diverse physiological pathways.

Dioxygenases play key roles in metabolism, detoxification, and environmental processes. They are widespread in bacteria, fungi, plants, and animals. In environmental biotechnology, dioxygenases enable aerobic degradation of aromatic pollutants, contributing to bioremediation and the synthesis of natural products. Their activity is central to carbon cycling and the biosynthesis of bioactive molecules.