Argininosuccinic Acid: This amino acid is formed during the urea cycle from citrulline, aspartate and ATP. This reaction is catalyzed by argininosuccinic acid synthetase.Argininosuccinic Aciduria: Rare autosomal recessive disorder of the urea cycle which leads to the accumulation of argininosuccinic acid in body fluids and severe HYPERAMMONEMIA. Clinical features of the neonatal onset of the disorder include poor feeding, vomiting, lethargy, seizures, tachypnea, coma, and death. Later onset results in milder set of clinical features including vomiting, failure to thrive, irritability, behavioral problems, or psychomotor retardation. Mutations in the ARGININOSUCCINATE LYASE gene cause the disorder.Argininosuccinate Lyase: An enzyme of the urea cycle which splits argininosuccinate to fumarate plus arginine. Its absence leads to the metabolic disease ARGININOSUCCINIC ACIDURIA in man. EC 126.96.36.199.Amino Acid Metabolism, Inborn Errors: Disorders affecting amino acid metabolism. The majority of these disorders are inherited and present in the neonatal period with metabolic disturbances (e.g., ACIDOSIS) and neurologic manifestations. They are present at birth, although they may not become symptomatic until later in life.Argininosuccinate Synthase: An enzyme of the urea cycle that catalyzes the formation of argininosuccinic acid from citrulline and aspartic acid in the presence of ATP. Absence or deficiency of this enzyme causes the metabolic disease CITRULLINEMIA in humans. EC 188.8.131.52.Arginine: An essential amino acid that is physiologically active in the L-form.