Catalyzes the eighth step in arginine biosynthesis. Also has a catabolic function as the first enzyme of citrulline utilization as nitrogen source via arginine and the reactions involved in the arginase pathway. ATP + L-aspartate + L-citrulline = 2-(N(omega)-L-arginino)succinate + AMP + diphosphate + H(+) Optimum pH is 7.5-8.0 for the forward reaction and 6.0-6.5 for the reverse reaction. Amino-acid biosynthesis; L-arginine biosynthesis; L-arginine from L-ornithine and carbamoyl phosphate: step 2/3. Homotetramer. Present with 1870 molecules/cell in log phase SD medium. Belongs to the argininosuccinate synthase family. Type 1 subfamily.