Detection of 5'-phosphoribosyl-4-(N-succinylcarboxamide)-5-aminoimidazole in urine by use of the Bratton-Marshall reaction: identification of patients deficient in adenylosuccinate lyase activity.

The Bratton-Marshall reaction can be used to identify patients with adenylosuccinate lyase deficiency. These patients excrete in their urine the dephosphorylated derivative of the de novo purine synthesis intermediate 5'-phosphoribosyl-4-(N-succinylcarboxamide)-5-aminoimidazole (SAICAR). The test described here depends on a coupling reaction of N-1-naphthylethylenediamine with diazotized ribosyl-4-(N-succinylcarboxamide)-5-aminoimidazole giving rise to a fast developing purple chromaphore with a maximum absorbance at 555 nm. Using the closely related compound ribosyl-5-amino-4-imidazolecarboxamide (AICA riboside) as a standard, concentrations as low as 1.0 microM produce a visible color change. The absorption at 555 nM of the azo compound increases as a linear function of the concentration of AICA riboside in the reaction. The use of a filter-paper dipstick for urine sampling and storage is also described. The two metabolites which are present in increased concentration in biological fluids of adenylosuccinate lyase deficient patients are stable on the dipstick for at least 60 days when stored at room temperature (25 degrees C).