Dihydroorotase
InterPro Protein Domain record
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description
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<p>Dihydroorotase belongs to MEROPS peptidase family M38 (clan MJ), and includes peptides classified as a non-peptidase homologues. DHOase catalyses the third step in the <i>de novo</i> biosynthesis of pyrimidine, the conversion of ureidosuccinic acid (N-carbamoyl-L-aspartate) into dihydroorotate. Dihydroorotase binds a zinc ion which is required for its catalytic activity [<cite idref="PUB00002652"/>].</p><p>In bacteria, DHOase is a dimer of identical chains of about 400 amino-acid residues (gene pyrC). In higher eukaryotes, DHOase is part of a large multi-functional protein known as 'rudimentary' in <taxon tax_id="7227">Drosophila melanogaster</taxon> and CAD in mammals and which catalyzes the first three steps of pyrimidine biosynthesis [<cite idref="PUB00000720"/>]. The DHOase domain is located in the central part of this polyprotein. In yeasts, DHOase is encoded by a monofunctional protein (gene URA4). However, a defective DHOase domain [<cite idref="PUB00001777"/>] is found in a multifunctional protein (gene URA2) that catalyzes the first two steps of pyrimidine biosynthesis.</p><p>The comparison of DHOase sequences from various sources shows [<cite idref="PUB00003725"/>] that there are two highly conserved regions. The first located in the N-terminal extremity contains two histidine residues suggested [<cite idref="PUB00001777"/>] to be involved in binding the zinc ion. The second is found in the C-terminal part. Members of this family of proteins are predicted to adopt a TIM barrel fold [<cite idref="PUB00004994"/>].</p><p>Dihydroorotase 'multifunctional complex type' <db_xref db="EC" dbkey="3.5.2.3"/>, in contrast to the homodimeric type of dihydroorotase found in <taxon tax_id="562">Escherichia coli</taxon>, tends to appear in a large multifunctional complex with aspartate transcarbamoylase. Homologous domains appear in multifunctional proteins of higher eukaryotes. In some species, including <taxon tax_id="303">Pseudomonas putida</taxon> and <taxon tax_id="287">Pseudomonas aeruginosa</taxon>, this protein is inactive but is required as a non-catalytic subunit of aspartate transcarbamoylase (ATCase). In these species, a second, active dihydroorotase is also present.</p>
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