In the Wacker/Forward LD assay, which conversion occurs?

• A. Lactate to Pyruvate
• B. Pyruvate to Lactate
• C. Lactate to Lactic Acid
• D. Pyruvate to Acetyl-CoA

Answer: (A)

In this assay the key point is the direction LDH operates to measure its activity. Lactate dehydrogenase catalyzes the oxidation of lactate to pyruvate, with NAD+ accepting electrons to form NADH. In the Wacker/Forward LD assay, this lactate-to-pyruvate conversion is what’s being tracked, so the substrate lactate is converted into pyruvate as the readout of enzyme activity. The other options describe different biochemical steps that aren’t the reaction LDH performs in this setup: pyruvate to lactate would be a reverse, lactate to lactic acid isn’t a redox change measured here, and pyruvate to acetyl-CoA is a different enzyme’s reaction altogether.