Which of the following best describes the function of glucose-6-phosphatase?

• A. It catalyzes the conversion of glucose to glucose-6-phosphate
• B. It hydrolyzes glucose-6-phosphate to release free glucose
• C. It phosphorylates glycogen to form glycogen-6-phosphate
• D. It converts pyruvate to acetyl-CoA

Answer: (B)

The function of glucose-6-phosphatase is best described as hydrolyzing glucose-6-phosphate to release free glucose. This enzyme is primarily found in the liver and to a lesser extent in the kidney, where it plays an essential role in glucose homeostasis.

When glucose-6-phosphate is produced from carbohydrates, it cannot be released directly into the bloodstream. Instead, glucose-6-phosphatase converts glucose-6-phosphate into free glucose, which can then enter the bloodstream to regulate blood sugar levels, especially during fasting or between meals. This process is vital during gluconeogenesis and glycogenolysis, enabling the liver to maintain adequate glucose levels.

The other choices describe processes that either do not involve glucose-6-phosphatase or misrepresent its function. For example, the conversion of glucose to glucose-6-phosphate is catalyzed by the enzyme hexokinase or glucokinase, not glucose-6-phosphatase. Similarly, phosphorylating glycogen is not a direct role of glucose-6-phosphatase, and the conversion of pyruvate to acetyl-CoA is carried out by the pyruvate dehydrogenase complex, further clarifying the specific function