Catalyzes the reversible cleavage of L-argininosuccinate to fumarate and L-arginine, an intermediate step reaction in the urea cycle mostly providing for hepatic nitrogen detoxification into excretable urea as well as de novo L-arginine synthesis in nonhepatic tissues (PubMed:11747433, PubMed:11747432, PubMed:9045711, PubMed:22081021, PubMed:2263616). Essential regulator of intracellular and extracellular L-arginine pools. As part of citrulline-nitric oxide cycle, forms tissue-specific multiprotein complexes with argininosuccinate synthase ASS1, transport protein SLC7A1 and nitric oxide synthase NOS1, NOS2 or NOS3, allowing for cell-autonomous L-arginine synthesis while channeling extracellular L-arginine to nitric oxide synthesis pathway (PubMed:22081021). 2-(N(omega)-L-arginino)succinate = fumarate + L-arginine Enzyme activity is regulated by acetylation. Amino-acid biosynthesis; L-arginine biosynthesis; L-arginine from L-ornithine and carbamoyl phosphate: step 3/3. Nitrogen metabolism; urea cycle; L-arginine and fumarate from (N(omega)-L-arginino)succinate: step 1/1. Homotetramer (PubMed:11747433). Forms tissue-specific complexes with ASS1, SLC7A1, HSP90AA1 and nitric oxide synthase NOS1, NOS2 or NOS3; the complex maintenance is independent of ASL catalytic function (By similarity). Acetylation modifies enzyme activity in response to alterations of extracellular nutrient availability. Acetylation increased with trichostin A (TSA) or with nicotinamide (NAM). Glucose increases acetylation by about a factor of 3 with decreasing enzyme activity. Acetylation on Lys-288 is decreased on the addition of extra amino acids resulting in activation of enzyme activity. The disease is caused by variants affecting the gene represented in this entry. The phenotype heterogeneity among patients is associated with interallelic complementation resulting in either complete loss of activity or partial regeneration of functional active sites in the heterotetrameric mutant protein. Belongs to the lyase 1 family. Argininosuccinate lyase subfamily.