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Located in liver cytosol, it is the fourth enzyme of the urea cycle and involved in the biosynthesis of arginine in all species and the production of urea in ureotelic species. [2] Mutations resulting in low activity of the enzyme increase levels of urea in the body and result in various side effects.
The enzyme endothelial nitric oxide synthase produces nitric oxide from arginine in endothelial cells. [9] Argininosuccinate synthetase and argininosuccinate lyase recycle citrulline, a byproduct of nitric oxide production, into arginine. Since nitric oxide is an important signaling molecule, this role of ASS is important to vascular physiology.
In argininosuccinic aciduria, the enzyme argininosuccinate lyase, involved in the conversion of arginino succinate to arginine within the urea cycle, is damaged or missing. The urea cycle cannot proceed normally, and nitrogen accumulates in the bloodstream in the form of ammonia.
Arginine is synthesized from citrulline in the urea cycle by the sequential action of the cytosolic enzymes argininosuccinate synthetase and argininosuccinate lyase. This is an energetically costly process, because for each molecule of argininosuccinate that is synthesized, one molecule of adenosine triphosphate (ATP) is hydrolyzed to adenosine ...
In arginylation, arginine (pictured above) is added to proteins. Arginylation is a post-translational modification in which proteins are modified by the addition of arginine (Arg) at the N-terminal amino group or side chains of reactive amino acids by the enzyme, arginyltransferase (ATE1). Recent studies have also revealed that hundreds of ...
Argininemia is an autosomal recessive urea cycle disorder where a deficiency of the enzyme arginase causes a buildup of arginine and ammonia in the blood.Ammonia, which is formed when proteins are broken down in the body, is toxic if levels become too high; the nervous system is especially sensitive to the effects of excess ammonia.
This enzyme catalyzes the first step in creatine biosynthesis, the combination of arginine and glycine to form guanidinoacetate, which also results in the formation or ornithine as a by product. These reactions take place primarily in the kidney and pancreas. The clinical manifestations of AGAT deficiency are caused by the decreased amounts of ...
The enzymes in the kidney will then catalyze ureagenesis, compensating somewhat for a decrease in arginase I activity in the liver. Due to this alternate method of removing excess arginine and ammonia from the bloodstream, subjects with arginase deficiency tend to have longer lifespans than those who have other urea cycle defects.