| Type: | Domain | Name: | Aspartate/ornithine carbamoyltransferase, carbamoyl-P binding |
| Description: | This entry contains two related enzymes: Aspartate carbamoyltransferase () (ATCase) catalyzes the conversion of aspartate and carbamoyl phosphate to carbamoylaspartate, the second stepin the de novobiosynthesis of pyrimidine nucleotides []. In prokaryotesATCase consists of two subunits: a catalytic chain (gene pyrB) and a regulatory chain (gene pyrI), while in eukaryotes it is a domain in a multi-functional enzyme (called URA2 in yeast, rudimentary in Drosophila, and CAD in mammals []) that also catalyzes other steps of the biosynthesis ofpyrimidines.Ornithine carbamoyltransferase () (OTCase) catalyzes the conversion of ornithine and carbamoyl phosphate to citrulline. In mammals this enzymeparticipates in the urea cycle [] and is located in the mitochondrialmatrix. In prokaryotes and eukaryotic microorganisms it is involved in the biosynthesis of arginine. In some bacterial species it is also involved in thedegradation of arginine [] (the arginine deaminase pathway).It has been shown [] that these two enzymes are evolutionary related. Thepredicted secondary structure of both enzymes are similar and there are some regions of sequence similarities. One of these regions includes threeresidues which have been shown, by crystallographic studies [], to beimplicated in binding the phosphoryl group of carbamoyl phosphate and may also play a role in trimerization of the molecules []. The carboxyl-terminal, aspartate/ornithine-binding domain is is described by . | Short Name: | Asp/Orn_carbamoyltranf_P-bd |
