arginase deficiencymedical dictionary

<biochemistry> Arginase is the fifth enzyme of the urea cycle and catalyses the hydrolysis of arginine to ornithine and urea as the final step in the detoxification of ammonia.

Deficiency of the enzyme results in hyperargininaemia and episodic hyperammonaemia, leading to moderate to severe mental retardation and spasticity. at least two isozymes of arginase exist in man. AI (the enzyme deficient in the disorder) is cytosolic and found primarily in liver and red blood cells, whereas AII is mitochondrial and found predominantly in kidney but also to a lesser extent in liver, brain, and other tissues.

While AII activity appears to be induced in AI deficiency, it is only partially effective in maintaining urea cycle function. The normal in vivo function of AII is unclear.

Arginase deficiency is diagnosed by observing high arginine concentrations on either qualitative or quantitative plasma or urine amino acid analysis. The diagnosis is confirmed by finding markedly decreased or absent arginase activity in an isotopic red blood cell enzymatic assay. The AI gene has been cloned, sequenced, and localised to human chromosome band 6q23.

(17 Dec 1997)

argil, argillaceous, argillite, arginase < Prev | Next > arginine, arginine 2-monooxygenase, arginine amidase

Bookmark with: icon icon icon icon iconword visualiser Go and visit our forums Community Forums