Nonfatal Hyperammonemic Encephalopathy as a Late Complication of Roux-en-Y Gastric Bypass

Figure 1

Urea cycle. Ammonia is the source of the first amino group in the urea cycle, required in the synthesis of carbamoyl phosphate (CPS), which happens in the hepatocyte mitochondria. The second amino group comes from glutamate in the formation of aspartate, which happens in the hepatocyte cytoplasm. This reaction produces α-ketoglutarate, which then becomes available for the Krebs cycle. The synthesis of argininosuccinate links the Krebs cycle and urea cycle. In the peripheral tissues, glutamate accepts free ammonia from amino acid catabolism. Glutamine transports ammonia from the peripheral tissues to the liver, where glutamine is broken back to glutamate and ammonia via glutaminase. AST, aspartate transaminase.