adenylylsuccinate lyase; an enzyme catalyzing the nonhydrolytic cleavage of adenylosuccinic acid producing AMP and fumarate and also of 4-(N-succinocarboxamido)-5-aminoimidazole nucleotide to yield fumarate and aminoimidazole carboxamide ribosyl-5-phosphate. Both are steps in purine nucleotide biosynthesis. Syn: adenylosuccinase, adenylylosuccinate lyase.