Dihydroorotate dehydrogenase, class 2 (IPR005719)

Short name: Dihydroorotate_DH_2

Overlapping homologous superfamilies

Family relationships


This entry represents the enzyme protein dihydroorotate dehydrogenase (also called quinone) exclusively for class 2. It includes members from bacteria, yeast, plants etc. The subfamilies 1 and 2 share extensive homology, particularly toward the C terminus. This subfamily has a longer N-terminal region.

Dihydroorotate dehydrogenase (DHOD), also known as dihydroorotate oxidase, catalyses the fourth step in de novo pyrimidine biosynthesis, the stereospecific oxidation of (S)-dihydroorotate to orotate, which is the only redox reaction in this pathway. DHODs can be divided into two mains classes: class 1 cytosolic enzymes found primarily in Gram-positive bacteria, and class 2 membrane-associated enzymes found primarily in eukaryotic mitochondria and Gram-negative bacteria [PMID: 9405053].

The class 1 DHODs can be further divided into subclasses 1A and 1B, which differ in their structural organisation and use of electron acceptors. The 1A enzyme is a homodimer of two PyrD subunits where each subunit forms a TIM barrel fold with a bound FMN cofactor located near the top of the barrel [PMID: 9655329]. Fumarate is the natural electron acceptor for this enzyme. The 1B enzyme, in contrast is a heterotetramer composed of a central, FMN-containing, PyrD homodimer resembling the 1A homodimer, and two additional PyrK subunits which contain FAD and a 2Fe-2S cluster [PMID: 11188687]. These additional groups allow the enzyme to use NAD(+) as its natural electron acceptor.

The class 2 membrane-associated enzymes are monomers which have the FMN-containing TIM barrel domain found in the class 1 PyrD subunit, and an additional N-terminal alpha helical domain [PMID: 10673429, PMID: 12220493]. These enzymes use respiratory quinones as the physiological electron acceptor.

GO terms

Biological Process

GO:0006207 'de novo' pyrimidine nucleobase biosynthetic process
GO:0055114 oxidation-reduction process

Molecular Function

GO:0004152 dihydroorotate dehydrogenase activity

Cellular Component

GO:0016020 membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.