Ornithine carbamoyltransferase (OTC) catalyzes the reversible transfer of the carbamoyl group from carbamoyl phosphate (CP) to the Nε atom of L-ornithine (ORN) to produce L-citrulline. There are two types of the enzyme – anabolic (aOTC) and catabolic (cOTC). Anabolic OTCes participate in the urea cycle and L-arginine biosynthesis. Catabolic OTCes are part of the catabolic arginine deiminase pathway found in a number of microorganisms. The reported structure is for the anabolic enzyme from food-borne pathogen Campylobacter jejuni. The structure has two trimers in the asymmetric unit.