nvolved in the catabolism of arginine. Catalyzes the phosphorolysis of citrulline, the reverse reaction of the biosynthetic one, yielding ornithine and carbamoyl phosphate which serve to generate ATP from ADP. carbamoyl phosphate + L-ornithine = H(+) + L-citrulline + phosphate Amino-acid degradation; L-arginine degradation via ADI pathway; carbamoyl phosphate from L-arginine: step 2/2. Dodecamer (tetramer of trimers). Belongs to the aspartate/ornithine carbamoyltransferase superfamily. OTCase family.