The oxidative phase of the pentose phosphate pathway (PPP) catalyzes the conversion of glucose 6-phosphate (G6P) to ribulose 5-phosphate. The enzyme that catalyzes this reaction is:a. Glucose 6-phosphate dehydrogenaseb. Glucose 6-phosphate epimerasec. Glucose 6-phosphate phosphorylase d. Glucose 6-phosphate kinasee. Glucose 6-phosphate lyase dismutase
a. Glucose 6-phosphate dehydrogenase
The correct answer is a. Glucose 6-phosphate dehydrogenase.
Glucose 6-phosphate dehydrogenase is the enzyme that catalyzes the first and rate-limiting step in the oxidative phase of the PPP. This reaction involves the oxidation of G6P to 6-phosphoglucono-δ-lactone and the reduction of NADP+ to NADPH. The NADPH generated in this reaction is an important cofactor in many biosynthetic processes, including fatty acid and nucleotide synthesis. Ribulose 5-phosphate is formed in subsequent steps of the oxidative phase of the PPP.
Glucose 6-phosphate epimerase is an enzyme that catalyzes the conversion of glucose 6-phosphate to fructose 6-phosphate, which is a reaction that occurs in the glycolysis pathway. Glucose 6-phosphate phosphorylase catalyzes the conversion of glucose 6-phosphate to glucose 1-phosphate in the glycogenolysis pathway. Glucose 6-phosphate kinase catalyzes the phosphorylation of glucose 6-phosphate to form fructose 6-phosphate in the glycolysis pathway. Finally, glucose 6-phosphate lyase dismutase is not an enzyme that exists in nature and is not involved in any metabolic pathways.
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