These two succinylpurines are the dephosphorylated derivatives of SAICA ribotide (SAICAR) and adenylosuccinate (S-AMP), the two substrates of adenylosuccinate lyase (ASL), which catalyzes an important reaction in the de novo pathway of purine biosynthesis.
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ASL catalyzes two distinct reactions in the synthesis of purine nucleotides, both of which involve the β-elimination of fumarate to produce either aminoimidazole carboxamide ribotide (AICAR) from SAICAR or adenosine monophosphate (AMP) from S-AMP.
The conversion of ATP, L-aspartate, and 5-aminoimidazole-4-carboxyribonucleotide (CAIR) to 5-aminoimidazole-4-(N-succinylcarboxamide) ribonucleotide, ADP, and phosphate by phosphoribosylaminoimidazolesuccinocarboxamide synthetase (SAICAR synthetase) represents the eighth step of de novo purine nucleotide biosynthesis.