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Argininosuccinate lyase is an intermediate enzyme in the urea synthesis pathway and its function is imperative to the continuation of the cycle. A non-functioning enzyme results in patients' accumulation of ammonia, argininosuccinate, and citrulline in the blood, and argininosuccinate is excreted in the urine. [9]
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.
Argininosuccinic aciduria (Deficiency of argininosuccinic acid lyase) Argininemia (Deficiency of arginase) Hyperornithinemia, hyperammonemia, homocitrullinuria (HHH) syndrome (Deficiency of the mitochondrial ornithine transporter) [8] [16] All urea cycle defects, except OTC deficiency, are inherited in an autosomal recessive manner.
The enzyme that catalyzes the reaction is argininosuccinate synthetase. [ 3 ] [ 4 ] Argininosuccinic acid is a precursor to fumarate in the citric acid cycle via argininosuccinate lyase .
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.
Argininosuccinate synthetase is an enzyme that in humans is encoded by the ASS1 gene. [ 5 ] [ 6 ] [ 7 ] The protein encoded by this gene catalyzes the penultimate step of the arginine biosynthetic pathway .
Arginine is then synthesized from citrulline in the urea cycle by the sequential action of the cytosolic enzymes argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL). References [ edit ]
In humans, argininosuccinate lyase (ASL) is a homotetrameric enzyme that can undergo intragenic complementation. An ASL disorder in humans can arise from mutations in the ASL gene, particularly mutations that affect the active site of the tetrameric enzyme. ASL disorder is associated with considerable clinical and genetic heterogeneity which is ...