Select the coupling enzyme used in the hexokinase method for glucose.

Select the coupling enzyme used in the hexokinase method for glucose.

• A. Glucose dehydrogenase
• B. Glucose-6-phosphatase
• C. Glucose-6-phosphate dehydrogenase
• D. Peroxidase

Answer: (C)

In the hexokinase–based glucose assay, the signal comes from linking the formation of glucose-6-phosphate to NADPH production. Hexokinase first phosphorylates glucose to glucose-6-phosphate using ATP. The glucose-6-phosphate is then oxidized by glucose-6-phosphate dehydrogenase, which reduces NADP+ to NADPH. The amount of NADPH formed is proportional to the glucose present and is detected spectrophotometrically, providing a measurable readout. This makes glucose-6-phosphate dehydrogenase the coupling enzyme used. Other enzymes wouldn’t create the same linked signal: glucose dehydrogenase would act directly on glucose, glucose-6-phosphatase would remove the phosphate group, and peroxidase is used in different colorimetric schemes rather than the hexokinase coupling step.

In the hexokinase–based glucose assay, the signal comes from linking the formation of glucose-6-phosphate to NADPH production. Hexokinase first phosphorylates glucose to glucose-6-phosphate using ATP. The glucose-6-phosphate is then oxidized by glucose-6-phosphate dehydrogenase, which reduces NADP+ to NADPH. The amount of NADPH formed is proportional to the glucose present and is detected spectrophotometrically, providing a measurable readout. This makes glucose-6-phosphate dehydrogenase the coupling enzyme used. Other enzymes wouldn’t create the same linked signal: glucose dehydrogenase would act directly on glucose, glucose-6-phosphatase would remove the phosphate group, and peroxidase is used in different colorimetric schemes rather than the hexokinase coupling step.