Catalyzes the second step of the urea cycle, the condensation of carbamoyl phosphate with L-ornithine to form L-citrulline. The urea cycle ensures the detoxification of ammonia by converting it to urea for excretion. carbamoyl phosphate + L-ornithine = H(+) + L-citrulline + phosphate Negatively regulated by lysine acetylation. Nitrogen metabolism; urea cycle; L-citrulline from L-ornithine and carbamoyl phosphate: step 1/1. Homotrimer. Acetylation at Lys-88 negatively regulates ornithine carbamoyltransferase activity in response to nutrient signals. Defects in Otc are the cause of the Sparse fur (spf) phenotype. Spf mouse have an OTCase with an overall decrease in activity, and altered substrate affinity. Belongs to the aspartate/ornithine carbamoyltransferase superfamily. OTCase family.