InterPro: IPR002292 Ornithine carbamoyltransferase

The ornithine carbamoyltransferases are a family of enzymes that catalyse the production of citrulline from carbamoyl-phosphate and ornithine [1]. This reaction is part of the arginine biosynthetic pathway, and in some organisms the reaction is also part of the arginine deaminase pathway [2]. In most prokaryotes, and some lower eukaryotes, the enzyme is found in the cytoplasm, but in higher eukaryotes, such as mammals, the enzyme is found in the mitochondrial matrix and functions as part of the urea cycle. In most organisms analysed to date, the enzyme has been shown to consist of a trimer of identical or nonidentical subunits [3]. Extensive similarity has been found within the ornithine carbamoyltransferase family, some of the conserved areas being important in catalysis [4].

The C-terminal region of these enzymes shows a degree of similarity to the aspartate carbamoyltransferases, which are also known to bind carbamoyl- phosphate [5]. This region contains a highly conserved Cys residue (in a His-Cys-Lys-Pro motif) implicated in ornithine binding [3].