This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
NADPH+, H+ is generated in the reaction catalyzed by 
Select and explain. 
A. LDH, B. G-6-PD, C. G-3-PD, D. Alcohol dehydrogenase
B: G-6-PD
Answer: B: G-6-PD 
Explanation: uThe limited metabolic pathways present in red blood cells renders them completely reliant on the pentose phosphate pathway or, to be more specific, the X-linked enzyme glucose-6-phosphate dehydrogenase for the reduction of NADP+ to NADPH. uReduced NADPH is needed for the reduction of GSSG to GSH, a key intracellular antioxidant, by the enzyme glutathione reductase. uA deficiency in glucose-6-phosphate dehydrogenase renders red blood cells hypersensitive to oxidative stress. uIndividuals harboring G-6-PD deficiency are vulnerable to attacks of hemolytic anemia, resulting from the inability to generate sufficient reduced glutathione to combat episodes of oxidative stress. Harper's illustrated Biochemistry , 30th ed , page 693