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 OTCs participate in the urea cycle and L-arginine biosynthesis. Catabolic OTCs are part of the catabolic arginine deiminase pathway found in a number of microorganisms. The reported structure is for the anabolic enzyme from pathogen Vibrio vulnificus. The structure has three monomers in the asymmetric unit which form the physiologically active trimer. All three enzyme subunits are entrapped in a complex with the products of the enzymatic reaction – L-citrulline and inorganic phosphate. The structure shows that binding of both products together causes closure of interdomain cleft and brings catalytic loops K*STRTR, B2–H3 and SMG into the catalytic site that adopt conformations same as in the the Michaelis complex.