<prompt> Lesh-Nyan syndrome is due to deficiency of: RepeatHGPRTaseCPS ICPS IIPRPP synthetase  <response>: Ans: A HGPRTase Ref: Harpers Illustrated Biochemistry, 29th edition. Page 335, 339 742Explanation:Lesh-Nyhan SyndromeThis syndrome is characterized by:HyperuricemiaUrolithiasisSelf mutilationCNS manifestationsExtrapyramidul involvement Choreathethosis, Dystonia, OphisthotonusEnzyme DefectHypoxanthine-guanine Phosphoribosyl Transferase HGPRTase.This enzyme is involved in purine salvage it converts hypoxanthine to inosine mono phosphate IMP.In absence of this enzyme intracellular PRPP levels will be elevated.Mutation in gene producing HGPRTase may be due to deletion, frame shift mutation, base substitutions or aberrent mRNA splicing.Note: Salvage reactions require less energy than the de novo synthesis. 