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Title: Lesch-Nyhan syndrome is a disease caused by severe deficiency in HPRT activit Post by: biolove on Nov 17, 2010 Lesch-Nyhan syndrome is a disease caused by severe deficiency in HPRT activity. In the absence of HPRT, hypoxanthine and guanine are not converted to IMP and GMP, respectively, in the salvage reactions. The disease is characterized by the accumulation of excessive amounts of uric acid, a product of nucleotide degradation, which causes neurological abnormalities and destructive behaviour, including self-mutilation. Explain why the absence of HPRT causes uric acid to accumulate.
Title: Re: Lesch-Nyhan syndrome is a disease caused by severe deficiency in HPRT activit Post by: bio_man on Nov 17, 2010 HPRT is required to convert hypoxanthine and guanine back into inosine monophosphate and guanosine monophosphate. If this does not occur, IMP and GMP will continue to be produced because their production is ultimately regulated by their concentrations inside the cell. Recall that both IMP and GMP inhibit glutamine PRPP amidotransferase and PRPP synthetase when their concentrations are high. Once produced, IMP and GMP will be degraded in inosine and guanosine, respectively, and then hypoxanthine and guanine. This unregulated cycle will increase the concentration of hypoxanthine because all purines are converted to xanthine. Xanthine is converted into uric acid by xanthine oxidase.
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