Select the enzyme that is most specific for beta-D-glucose.

Select the enzyme that is most specific for beta-D-glucose.

• A. Glucose oxidase
• B. Glucose-6-phosphate dehydrogenase
• C. Hexokinase
• D. Phosphohexose isomerase

Answer: (A)

Substrate specificity for the beta anomer of glucose. In solution, glucose exists as alpha and beta forms (mutarotation), but some enzymes are highly selective for one form. Glucose oxidase binds and oxidizes beta-D-glucose specifically to D-glucono-1,5-lactone, producing hydrogen peroxide in the process. This tight preference for the beta form makes it the most specific enzyme for beta-D-glucose. The other enzymes act on different substrates or forms: some require phosphorylated glucose rather than free glucose, and others act on glucose-6-phosphate rather than the beta form of glucose, so they don’t exhibit the same beta-specificity.

Substrate specificity for the beta anomer of glucose. In solution, glucose exists as alpha and beta forms (mutarotation), but some enzymes are highly selective for one form. Glucose oxidase binds and oxidizes beta-D-glucose specifically to D-glucono-1,5-lactone, producing hydrogen peroxide in the process. This tight preference for the beta form makes it the most specific enzyme for beta-D-glucose.

The other enzymes act on different substrates or forms: some require phosphorylated glucose rather than free glucose, and others act on glucose-6-phosphate rather than the beta form of glucose, so they don’t exhibit the same beta-specificity.