InterPro domain: IPR023434

Argininosuccinate synthase ( 6.3.4.5 ) (AS) is a urea cycle enzyme that catalyzes the penultimate step in arginine biosynthesis: the ATP-dependent ligation of citrulline to aspartate to form argininosuccinate, AMP and pyrophosphate [ 1 , 2 ].

In humans, a defect in the AS gene causes citrullinemia, a genetic diseasecharacterised by severe vomiting spells and mental retardation.

AS is a homotetrameric enzyme of chains of about 400 amino-acid residues. An arginine seems to be important for the enzyme's catalytic mechanism. The sequences of AS from various prokaryotes, archaebacteria and eukaryotes show significant similarity.

This entry represents argininosuccinate synthase, type 1 subfamily.

1. Sequences of the genes encoding argininosuccinate synthetase in Escherichia coli and Saccharomyces cerevisiae: comparison with methanogenic archaebacteria and mammals. Gene 95, 99-104
2. Conservation of structure in the human gene encoding argininosuccinate synthetase and the argG genes of the archaebacteria Methanosarcina barkeri MS and Methanococcus vannielii. J. Bacteriol. 170, 3125-30