[PRPP synthetase superactivity].

Phosphoribosylpyrophosphate(PRPP) synthetase(PRS) catalyzes the formation of PRPP from ATP and ribose-5-phosphate. PRPP is an important substrate for the synthesis of purine, pyrimidine, and pyridine dinucleotides. Human PRS exists as complex aggregates composed of the 34 kDa catalytic subunits(PRS1 and PRS2) and other 39 kDa component designated PRPP synthetase-associated protein (PAP39). PRS superactivity is an X-chromosome linked disorder, characterized by gout and uric acid overproduction resulting from accelerated synthesis of PRPP and purine nucleotides. Among the nearly 30 affected families identified to date, there are several families in which PRS superactivity with purine nucleotide feedback resistance are associated with neurodevelopmental abnormalities in addition to hyperuricemia and gout. Different nucleotide substitutions in the PRPS1 gene encoding PRS1 have identified in six unrelated affected families with purine nucleotide feedback-resistant PRS superactivity.