A group of diseases related to a deficiency of the enzyme ARGININOSUCCINATE SYNTHASE which causes an elevation of serum levels of CITRULLINE. In neonates, clinical manifestations include lethargy, hypotonia, and SEIZURES. Milder forms also occur. Childhood and adult forms may present with recurrent episodes of intermittent weakness, lethargy, ATAXIA, behavioral changes, and DYSARTHRIA. (From Menkes, Textbook of Child Neurology, 5th ed, p49)

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 6.3.4.5.

Citrulline is an α-amino acid, primarily produced in the urea cycle in the liver and found in some dietary proteins, which functions as a vital intermediator in the nitrogen metabolism and vasodilation, and can be supplemented for potential health benefits in improving blood flow, reducing fatigue, and enhancing exercise performance.

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.

The sodium salt of BENZOIC ACID. It is used as an antifungal preservative in pharmaceutical preparations and foods. It may also be used as a test for liver function.

Elevated level of AMMONIA in the blood. It is a sign of defective CATABOLISM of AMINO ACIDS or ammonia to UREA.

A pancreatic trypsin inhibitor common to all mammals. It is secreted with the zymogens into the pancreatic juice. It is a protein composed of 56 amino acid residues and is different in amino acid composition and physiological activity from the Kunitz bovine pancreatic trypsin inhibitor (APROTININ).

A thyroid hormone transport protein found in serum. It binds about 75% of circulating THYROXINE and 70% of circulating TRIIODOTHYRONINE.

A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as AMMONIUM HYDROXIDE.

Proteins involved in the transport of specific substances across the membranes of the MITOCHONDRIA.

A class of enzymes that catalyze the formation of a bond between two substrate molecules, coupled with the hydrolysis of a pyrophosphate bond in ATP or a similar energy donor. (Dorland, 28th ed) EC 6.