|Superclasses:||Reactions Classified By Conversion Type → Simple Reactions → Chemical Reactions → Composite Reactions → Electron-Transfer-Reactions|
|Reactions Classified By Substrate → Small-Molecule Reactions|
EC Number: 18.104.22.168
Enzymes and Genes:
|Arabidopsis thaliana col :||dihydroorotate dehydrogenase
In Pathway: UMP biosynthesis
Supersedes EC number: 22.214.171.124
Reaction Locations: inner membrane (sensu Gram-negative Bacteria)
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.
Mass balance status: Balanced.
(S)-dihydroorotate[in] + a ubiquinone[membrane] → orotate[in] + an ubiquinol[membrane] (126.96.36.199)
(S)-dihydroorotate + a menaquinone[inner membrane] → orotate + a menaquinol[inner membrane] (188.8.131.52)
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
Standard Gibbs Free Energy (ΔrG'° in kcal/mol): 2.2177582 [Latendresse13]
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 184.108.40.206), NAD+ (EC 220.127.116.11) or NADP+ (EC 18.104.22.168) as electron acceptor.
Instance reaction of [(S)-dihydroorotate + an electron-transfer quinone[inner membrane] → orotate + an electron-transfer quinol[inner membrane]] (22.214.171.124):
i1: (S)-dihydroorotate[in] + a ubiquinone[membrane] → orotate[in] + an ubiquinol[membrane] (126.96.36.199)
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
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