In the lactate dehydrogenase (LDH) assay, the reaction depends on which coenzyme system?

In the lactate dehydrogenase (LDH) assay, the reaction depends on which coenzyme system?

• A. NAD/NADH
• B. ATP/ADP
• C. Fe++/Fe+++,
• D. Cu/Cu++

Answer: (A)

The key idea is that lactate dehydrogenase uses the NAD+/NADH coenzyme system. In the reaction, lactate is oxidized to pyruvate, and NAD+ accepts a hydride to become NADH. Measuring the amount of NADH formed (often by its absorbance at 340 nm) reflects LDH activity in the assay. The other substances listed aren’t involved in this redox step: ATP/ADP is the energy currency for kinases, not LDH; Fe or Cu ions serve as cofactors for other enzymes, but not the LDH dehydrogenase reaction.

The key idea is that lactate dehydrogenase uses the NAD+/NADH coenzyme system. In the reaction, lactate is oxidized to pyruvate, and NAD+ accepts a hydride to become NADH. Measuring the amount of NADH formed (often by its absorbance at 340 nm) reflects LDH activity in the assay. The other substances listed aren’t involved in this redox step: ATP/ADP is the energy currency for kinases, not LDH; Fe or Cu ions serve as cofactors for other enzymes, but not the LDH dehydrogenase reaction.