What are the products of the initial reaction when beta-D-glucose is oxidized by glucose oxidase?

• A. Glucuronic acid + H2O2
• B. Glucose-6-phosphate + NAD+
• C. Glucuronic acid + NADH
• D. Glucose-6-phosphate + H2O2

Answer: (A)

Glucose oxidase oxidizes the aldehyde group of beta-D-glucose to a carboxyl group, forming D-glucono-δ-lactone which rapidly hydrolyzes to D-gluconic acid, and in this process molecular oxygen is reduced to hydrogen peroxide. So the initial reaction products are gluconic acid (or its lactone form) and hydrogen peroxide. Among the given options, the one that lists hydrogen peroxide as a product aligns with this key byproduct of the enzyme-catalyzed reaction, making it the best match. Note that the acid produced is gluconic acid, not glucuronic acid, but the presence of H2O2 is the defining clue here.