Oxidation of amino acid-derived acetyl-CoA to water and CO
via the Krebs cycle and the role of the urea cycle to synthesize urea from ammonia in pigs. In animals, amino acids are utilized to produce proteins (including enzymes), small peptides, other nitrogenous metabolites (e.g., nitric oxide, creatine, carnitine, and ammonia), fatty acids, and glucose. Ammonia plays an important role in bridging the Krebs cycle with the urea cycle. AA, amino acids; ASL, argininosuccinate lyase; ASS, argininosuccinate synthase; CPS-1, carbamoylphosphate synthetase-I; GABA, γ-aminobutyrate; NAG, N-acetylglutamate; NPNM, non-peptide nitrogenous metabolites; and OCT, ornithine carbamoyltransferase.