Overview Three possible fates enter citric acid cycle form ketone bodies substrates for gluconeogenesis Urea cycle function degrade excess amino acids and safely remove nitrogen login to view 1 more bullet produce urea pathway aspartate and carbamoyl phosphate provide nitrogens login to view 4 more bullets nitrogen added from systemic pool via alanine cycle one turn of the cycle: login to view 1 more bullet connected to citric acid cycle login to view 3 more bullets location cellularly login to view 2 more bullets systemic login to view 1 more bullet deficiencies common presentation login to view 6 more bullets carbamoyl phosphate synthase I creates carbamoyl phosphate login to view 2 more bullets ornithine transcarbamoylase forms citrulline from carbamoyl phosphate login to view 3 more bullets treatment login to view 3 more bullets Ammonia transport function safely move nitrogenous wastes from tissues to kidney and intestine in the form of glutamine pathway ammonia loaded via glutamine synthetase login to view 2 more bullets ammonia unloaded via glutaminase login to view 3 more bullets Glucose-alanine cycle function transport pyruvate from muscle to liver for gluconeogenesis pathway involves reversible aminotransferase reactions login to view 9 more bullets relationship between amino acids andα-keto acids alanine - NH3 = pyruvate aspartate - NH3 = oxaloacetate glutamate - NH3 = α-ketoglutarate Defects in specific amino acid catabolism all are part of newborn screening program phenylketonuria (PKU) inability to break down phenylalanine login to view 2 more bullets presentation login to view 5 more bullets restriction of phenylalanine in the diet login to view 3 more bullets maple syrup urine disease inability to breakdown branched-chain amino acids (Val, Leu, Ile) login to view 1 more bullet presentation login to view 9 more bullets alkaptonuria inability to breakdown homogentisic acid (breakdown product of tyrosine and phenylalanine) login to view 1 more bullet presentation login to view 5 more bullets Hartnup's disease deficiency of neutral amino acid transporter login to view 1 more bullet presentation login to view 2 more bullets homocystinuria inability to breakdown homocystinuria (methionine degradation pathway) login to view 5 more bullets presentation login to view 11 more bullets treatment varies by cause login to view 4 more bullets propionyl-CoA carboxylase/methylmalonyl-CoA deficiency inability to handle Val, Met, Ile, Thr part of propionic acid pathway presentation login to view 3 more bullets treat by restricting Val, Met, Ile, Thr in the diet