Abstract
Adenylosuccinase (adenylosuccinate lyase, EC 4.3.2.2: ASase) catalyses two steps in the purine metabolic pathways: a) the eighth step in the de novo pathway of purine synthesis: conversion of succinylaminoimidazole carboxamide ribotide (SAICAR) into aminoimidazole carboxamide ribotide (AICAR) and b) the second step in the formation of adenyl nucleotides from IMP: conversion of adenylosuccinate (S-AMP) into AMP. As a result of the enzyme deficiency, there is a recognised accumulation of the two dephosphorylated substrates of the enzyme: SAICA riboside and succinyladenosine (S-Ado). Dephosphorylation of SAICAR and S-AMP is performed by cytosolic 5′nucleotidases. Neither SAICA riboside nor S-Ado are normally detectable in the blood or tissue samples of humans, but in patients with ASase deficiency, both compounds are present in the urine, blood and CSF. In the latter, concentrations are usually around 100-200 μM (Jaeken et al., 1993).
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