This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
The cause of hyperuricemia and gout in glucose-6- phosphatase deficiency is 
Select and explain. 
A. More formation of pentose, B. Decreased availability of glucose to tissues, C. Increased accumulation of sorbitol, D. Impaired degradation of free radicals
A: More formation of pentose
Answer: A: More formation of pentose 
Explanation: Purine overproduction and hyperuricemia in von Gierke disease (glucose-6-phosphatase deficiency) occurs secondary to enhanced generation of PRPP precursor, i.e. ribose-5-phosphate (a pentose).
In glucose-6-phosphatase deficiency, glucose-6-phosphate cannot be converted to glucose. Accumulated glucose-6-phosphate is then metabolized via HMP shunt, which in turn generates large amounts of ribose-5-phosphate, a precursor of PRPP. The increased synthesis of PRPP then enhances de novo synthesis of purine nucleotides.