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What is Which of the following is not true about hypoxanthineguanine phosphoribosyl transferase? and explain in detail?
"SALVAGE REACTIONS" CONVE PURINES & THEIR NUCLEOSIDES TO MONONUCLEOTIDES Conversion of purines, their ribonucleosides, and their deoxyribonuc]eosides to mononucleotides involves so- called "salvage reactions" that require far less energy than de novo synthesis. The more impoant mechanism involves phosphoribosylation by PRPP of a free punine (Pu) to form a purine 5'-mononucleotide (Pu-RP). Three processes contribute to purine nucleotide biosynthesis. These are, in order of decreasing impoance: (1) Synthesis from amphibolic intermediates (synthesis de novo), (2) Phosphoribosyltion of purines, and (3) Phosphorylation of purine nucleosides. Lesch-Nyhan Syndrome * X-linked recessive. * Overproduction hyperuricemia. * Purine salvage problem owing to absence of HGP, which conves hypoxanthine to IMP and guanine to GMP. * C/f: o Mental retardation, o Self-mutilation, aggression, o Hyperuricemia, gout, and o Choreoathetosis. * Reflects a defect in hypoxanthine-guanine phosphoribosyl transferase (HGPase), an enzyme of purine salvage. * The accompanying rise in intracellular PRPP results in purine overproduction. * Mutations that decrease or abolish hypoxanthine-guanine phosphoribosyl transferase activity include deletions, frame-shift mutations, base substitutions, and aberrant mRNA splicing.