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Old 07-27-2014
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Default A 2-year-old boy with mental retardation

A 2-year-old boy with mental retardation has chewed the tips of his fingers on both hands and a portion of his lower lip. His serum uric acid concentration is increased, and he has a history of uric acid renal calculi. His 5-year-old brother has similar findings. Which of the following abnormal enzyme activities is the most likely cause of these findings?

(A) Decreased adenine phosphoribosyltransferase
(B) Decreased adenosine deaminase
(C) Decreased hypoxanthine-guanine phosphoribosyltransferase
(D) Increased phosphoribosylpyrophosphate synthetase
(E) Increased xanthine oxidase
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Old 07-27-2014
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c- HGPRT deficiency- Lesch Nyhan syndrome. this enzyme catalyses the reaction of Hypoxanthine to IMP and Guanine to GMP ( purine salvage pathway)... without this enzyme, guanine and hypoxanthine are directed to increased uric acid production
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