In the lactate dehydrogenase (LDH) assay, which product is measured?

In the lactate dehydrogenase (LDH) assay, which product is measured?

• A. NADH
• B. ATP
• C. Lactic Acid
• D. Pyruvic Acid

Answer: (A)

The readout in an LDH assay comes from NADH formation. Lactate dehydrogenase catalyzes the conversion of lactate to pyruvate with the simultaneous reduction of NAD+ to NADH. In the common spectrophotometric setup, NADH is measured because it has a strong absorbance at 340 nm while NAD+ does not. The amount of NADH produced is proportional to LDH activity, making NADH the product that is actually detected. If the assay were run in the reverse direction, one would monitor NADH consumption (a decrease in absorbance), but the typical readout is NADH formation.

The readout in an LDH assay comes from NADH formation. Lactate dehydrogenase catalyzes the conversion of lactate to pyruvate with the simultaneous reduction of NAD+ to NADH. In the common spectrophotometric setup, NADH is measured because it has a strong absorbance at 340 nm while NAD+ does not. The amount of NADH produced is proportional to LDH activity, making NADH the product that is actually detected. If the assay were run in the reverse direction, one would monitor NADH consumption (a decrease in absorbance), but the typical readout is NADH formation.