Escherichia coli K-12 substr. MG1655 Reaction:

Superclasses: Reactions Classified By Conversion TypeSimple ReactionsChemical ReactionsComposite ReactionsElectron-Transfer-Reactions
Reactions Classified By SubstrateSmall-Molecule Reactions

EC Number:

Enzymes and Genes:
dihydroorotate dehydrogenase, type 2Inferred from experiment: pyrD

In Pathway: UMP biosynthesis

Supersedes EC number:

Note that this reaction equation differs from the official Enzyme Commission reaction equation for this EC number, which can be found here .

Transport reaction diagram

Reaction Locations: inner membrane (sensu Gram-negative Bacteria)

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the Enzyme Commission system.

Mass balance status: Balanced.

Direct generic reaction:
(S)-dihydroorotate + an electron-transfer quinone[inner membrane] → orotate + an electron-transfer quinol[inner membrane] (

Enzyme Commission Primary Name: dihydroorotate dehydrogenase (quinone)

Enzyme Commission Synonyms: dihydroorotate:ubiquinone oxidoreductase, (S)-dihydroorotate:(acceptor) oxidoreductase, (S)-dihydroorotate:acceptor oxidoreductase, DHOdehase (ambiguous), DHOD (ambiguous), DHODase (ambiguous), DHODH

Enzyme Commission Summary:
This Class 2 dihydroorotate dehydrogenase enzyme contains FMN [Fagan06]. The enzyme is found in eukaryotes in the mitochondrial membrane and in some Gram negative bacteria associated with the cytoplasmic membrane [Hines86, Bjornberg99]. The reaction is the only redox reaction in the de-novo biosynthesis of pyrimidine nucleotides [Hines86, Fagan06]. The best quinone electron acceptors for the enzyme from bovine liver are coenzymes ubiquinone-6 and ubiquinone-7, although simple quinones, such as benzoquinone, can also act as acceptor but at lower rates [Hines86]. Methyl-, ethyl-, tert-butyl and benzyl-(S)-dihydroorotates are also substrates, but 1- and 3-methyl and 1,3-dimethyl methyl-(S)-dihydroorotates are not [ [Hines86]. Class 1 dihydroorotate dehydrogenases use either fumarate ( EC, NAD+ ( EC or NADP+ ( EC as electron acceptor.

Citations: [Forman78, Bader98]

Gene-Reaction Schematic

Gene-Reaction Schematic

Relationship Links: BRENDA:EC:, ENZYME:EC:, IUBMB-ExplorEnz:EC:

Created 15-Jul-2010 by Keseler I, SRI International


Bader98: Bader B, Knecht W, Fries M, Loffler M (1998). "Expression, purification, and characterization of histidine-tagged rat and human flavoenzyme dihydroorotate dehydrogenase." Protein Expr Purif 13(3);414-22. PMID: 9693067

Bjornberg99: Bjornberg O, Gruner AC, Roepstorff P, Jensen KF (1999). "The activity of Escherichia coli dihydroorotate dehydrogenase is dependent on a conserved loop identified by sequence homology, mutagenesis, and limited proteolysis." Biochemistry 38(10);2899-908. PMID: 10074342

Fagan06: Fagan RL, Nelson MN, Pagano PM, Palfey BA (2006). "Mechanism of flavin reduction in class 2 dihydroorotate dehydrogenases." Biochemistry 45(50);14926-32. PMID: 17154530

Forman78: Forman HJ, Kennedy J (1978). "Mammalian dihydroorotate dehydrogenase: physical and catalytic properties of the primary enzyme." Arch Biochem Biophys 191(1);23-31. PMID: 216313

Hines86: Hines V, Keys LD, Johnston M (1986). "Purification and properties of the bovine liver mitochondrial dihydroorotate dehydrogenase." J Biol Chem 261(24);11386-92. PMID: 3733756

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of EcoCyc: Nucleic Acids Research 41:D605-12 2013
Page generated by SRI International Pathway Tools version 19.5 on Fri Nov 27, 2015, BIOCYC13B.