oxypurinol and Purine-Pyrimidine-Metabolism--Inborn-Errors

A 60-year-old Japanese man was diagnosed as having hypouricemia at an annual health check-up. The routine laboratory data was not remarkable except that the patient's hypouricemia and plasma levels of xanthine and hypoxanthine were much higher than those of normal subjects. Furthermore, the patient's daily urinary excretion of xanthine and hypoxanthine was markedly increased compared with reference values. The xanthine dehyrogenase activity of the duodenal mucosa was below the limits of detection. Nevertheless, allopurinol was metabolized to oxypurinol in vivo. Based on these findings, a subtype of classical xanthinuria (type I) was diagnosed. The xanthine dehyrogenase protein was detected by Western blotting analysis. Sequencing of the cDNA of the xanthine dehyrogenase obtained from the duodenal mucosa revealed that a point mutation of C to T had occurred in nucleotide 445. This changed codon 149 from CGC (Arg) to TGC (Cys), a finding that has not been previously reported in patients with classical xanthinuria type I.

Topics: Allopurinol; Humans; Hypoxanthine; Male; Middle Aged; Oxypurinol; Point Mutation; Purine-Pyrimidine Metabolism, Inborn Errors; Sequence Analysis, DNA; Xanthine; Xanthine Dehydrogenase

Two brothers with classical xanthinuria who lacked xanthine dehydrogenase activity were encountered. Their hypouricemia was caused by underproduction of uric acid. In their duodenal mucosa, no xanthine dehydrogenase (oxidase) activity was detected. The patients had no symptoms except for duodenal ulcer in one case. The conversion of allopurinol to oxipurinol during an allopurinol loading test for determining the type of classical xanthinuria revealed that the patients had classical type 1 xanthinuria, because aldehyde oxidase activity was present. Furthermore, the allopurinol loading test was conducted to determine the optimal examination times and specimens required for this test.

Topics: Adult; Allopurinol; Humans; Male; Mutation; Oxypurinol; Purine-Pyrimidine Metabolism, Inborn Errors; Uric Acid; Xanthine Dehydrogenase; Xanthines

Genetic heterogeneity has been suggested in xanthinuria from the hitherto unexplained ability of some patients with this hereditary disorder to convert allopurinol to its active metabolite oxipurinol--an activity generally attributed to xanthine oxidase. This study provides evidence that the enzyme aldehyde oxidase is also deficient in xanthinuric patients not converting allopurinol to oxipurinol, whereas a xanthinuric patient with normal formation of oxipurinol had normal aldehyde oxidase activity. It is concluded that the enzyme aldehyde oxidase is the principal enzyme responsible for the formation of oxipurinol in man.

Topics: Adult; Aldehyde Oxidase; Aldehyde Oxidoreductases; Allopurinol; Humans; Male; Middle Aged; Oxypurinol; Purine-Pyrimidine Metabolism, Inborn Errors; Pyrimidines; Xanthine Oxidase; Xanthines

We used a reversed-phase "high-performance" liquid-chromatographic system equipped with a multichannel ultraviolet spectrometric detector and a micro-computer for analyzing urine samples from patients with disorders of purine metabolism. This system recorded a series of absorption-spectrum data from a single chromatographic run and stored them for subsequent analysis. Because the retention times and ultraviolet absorption spectra of the eluates were recorded simultaneously, identification of peaks was easy and quite accurate for simultaneous quantification of orotidine, adenine, hypoxanthine, uric acid, xanthine, allopurinol (4-hydroxypyrazolo[3,4-d]pyrimidine), oxypurinol (4,6-dihydroxypyrazolo[3,4-d]pyrimidine), inosine, and 2,8-dihydroxyadenine--compounds extremely difficult or even impossible to quantify simultaneously with a conventional single-wavelength spectrometer. We used this method to investigate purine metabolites in urines from a patient with hereditary xanthinuria, three patients with 2,8-dihydroxyadenine urolithiasis, and a gouty subject taking allopurinol.

Topics: Adenine; Allopurinol; Chromatography, High Pressure Liquid; Humans; Hypoxanthine; Hypoxanthines; Inosine; Oxypurinol; Purine-Pyrimidine Metabolism, Inborn Errors; Purines; Spectrophotometry, Ultraviolet; Uric Acid; Uridine; Xanthine; Xanthines

Allopurinol-1-riboside, a major metabolite of allopurinol, is commonly thought to be directly synthesized by purine nucleoside phosphorylase (PNP) in vivo. As this enzyme is otherwise believed to function in vivo primarily in the direction of nucleoside breakdown, we have determined by high performance liquid chromatography and a conventional chromatographic method the urinary metabolites of allopurinol in a child deficient of PNP. In this patient approximately 40% of urinary allopurinol metabolites consisted of allopurinol-1-riboside, thus proving the possibility of indirect formation of allopurinol-1-riboside via allopurinol-1-ribotide in vivo, catalysed by hypoxanthine guanine phosphoribosyltransferase (HGPRT) and a phosphatase.

Topics: Allopurinol; Chromatography, Affinity; Chromatography, High Pressure Liquid; Guanine; Humans; Hypoxanthine Phosphoribosyltransferase; Infant; Male; Oxypurinol; Pentosyltransferases; Purine-Nucleoside Phosphorylase; Purine-Pyrimidine Metabolism, Inborn Errors; Ribonucleosides

Topics: Aspartate Aminotransferases; Female; Humans; Male; Middle Aged; Oxypurinol; Purine-Pyrimidine Metabolism, Inborn Errors; Uric Acid; Xanthines