Disorders of Purine Metabolism Disorder

Disorders of Purine Metabolism Disorder Defect Nature of Defect Comments 3 different enzyme defects can lead to gout: Gout PRPP synthetase elevated activity hyperuricemia HGPRTa deficiency glucose-6 -phosphatase deficiency Lesch-Nyhan syndrome HGPRT lack of enzyme see above SCID ADAb lack of enzyme see above Immunodeficiency PNPc lack of enzyme see above Renal lithiasis APRTd lack of enzyme 2, 8 -dihydroxyadenine, renal lithiasis hypouricemia and xanthine renal Xanthinuria Xanthine oxidase lack of enzyme lithiasis von Gierke disease Glucose-6 -phosphatase enzyme deficiency see above

Disorders of Pyrimidine Metabolism Disorder Defective Enzyme Comments orotate phosphoribosyl transferase and OMP Orotic aciduria, Type I see above decarboxylase Orotic aciduria, Type II OMP decarboxylase see above increased mitochondrial carbamoyl phosphate exits and Orotic aciduria due to OTC deficiency the urea cycle enzyme, ornithine transcarbamoylase, is augments pyrimidine biosynthesis; hepatic (no hematologic component) deficient encephalopathy transaminase, affects urea cycle function during β-aminoisobutyric aciduria benign, frequent in Orientals deamination of α-amino acids to α-keto acids allopurinol and 6 -azauridine treatments cause orotic drug induced orotic aciduria OMP decarboxylase acidurias without a hematologic component; their catabolic by-products inhibit OMP decarboxylase