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Enzyme Classifications
EC, category 1.14.-.- monooxygenase
Response type Transfer of an oxygen atom
EC, category 1.13.-.- dioxygenase
Response type Transfer of two oxygen atoms

Oxygenases are enzymes that transfer one or more oxygen atoms to their substrate , with ring openings often also taking place on the aromatic molecule . Most of the time, NADP / NADPH is consumed. In contrast to oxidases , oxygenases catalyze oxidations, in which oxygen atoms are incorporated directly into the substrate molecule, with a new hydroxyl group or carboxy group being formed, for example . Depending on whether only one oxygen atom or both are built into the substrate, the oxygenases are divided into monooxygenases or dioxygenases.


Monooxygenases almost always consume NADPH and are often dependent on FAD and / or Fe 2+ (an exception is e.g. dopamine beta-hydroxylase , which uses ascorbate as an electron donor .) In the catalyzed reaction, exactly one oxygen atom of an oxygen molecule ( O 2 ) transferred to the substrate. Monooxygenases are also considered to be mixed-function oxygenases, since, in addition to transferring one oxygen atom, they reduce a second oxygen atom to water (H 2 O).

Catalyzed reactions:


Dioxygenases are enzymes that transfer both atoms of an oxygen molecule (O 2 ) to a substrate. Dioxygenases often consume NADH or NADPH and are often dependent on FAD and / or Fe 2+ .

Catalyzed reactions:



Mono- and dioxygenases are used extensively by bacteria to break down aromatic compounds and are therefore of fundamental importance for the carbon cycle of the biosphere .

See also


  • O. Hayaishi, M. Katagiri, S. Rothberg: Mechanism of the pyrocatechase reaction. In: J. Am. Chem. Soc. 77, 1955, pp. 5450-5451.
  • SG Sligar, TM Makris, IG Denisov: Thirty years of microbial P450 monooxygenase research: peroxo-heme intermediates - the central bus station in heme oxygenase catalysis. In: Biochem. Biophys. Res. Commun. 338 (1), 2005, pp. 346-354. doi: 10.1016 / j.bbrc.2005.08.094 . PMID 16139790 .
  • O. Hayaishi: An odyssey with oxygen ". Biochem. Biophys. In: Res. Commun. 338 (1), 2005, pp. 2-6. Doi: 10.1016 / j.bbrc.2005.09.019 . PMID 16185652 .
  • HS Mason, WK Fowlks, E. Peterson: Oxygen transfer and electron transport by the phenolase complex. In: J. Am. Chem. Soc. 77 (10), 1955, pp. 2914-2915.
  • MR Waterman: Professor Howard Mason and oxygen activation. In: Biochem. Biophys. Res. Commun. 338 (1), 2005, pp. 7-11. doi: 10.1016 / j.bbrc.2005.08.120 . PMID 16153596 .
  • TDH Bugg: Dioxygenase enzymes: catalytic mechanisms and chemical models. In: Tetrahedron. 59 (36), 2003, pp. 7075-7101. doi: 10.1016 / S0040-4020 (03) 00944-X .

Web links

Individual evidence

  1. a b Entry oxygenases in the Lexicon of Biochemistry at Spektrum Akademischer Verlag, Heidelberg