This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Disorders of Amino acid Metabolism, Subject name: Pediatrics
Hyperuricemia is caused in newborn due to defect in: 
Select and explain. 
A. Adenosine deaminase, B. Ornithine transcarbamylase, C. Xanthine oxidase, D. Hypoxanthine guanine ribosyltransferase
D: Hypoxanthine guanine ribosyltransferase
Answer: D: Hypoxanthine guanine ribosyltransferase 
Explanation: Plasma uric acid is elevated in Lesch Nyhan disease (Hypoxanthine guanine ribosyltransferase deficiency) Xanthine oxidase deficiency- plasma uric acid | Adenosine deaminase deficiency leads to hypouricemia. Ornithine transcarbamylase deficiency- | ammonia