Which method uses UV-spectrophotometry for transaminase determination?

• A. Reitman Frankel
• B. Karmen/AST or Walker/ALT
• C. Both
• D. None

Answer: (B)

The key idea is how the assay is read. Transaminase activity can be measured by coupling the reaction to NADH oxidation and watching NADH disappear at 340 nm, which is in the UV range. The Karmen method for AST and the Walker method for ALT use this approach: AST produces oxaloacetate, which is reduced to malate by malate dehydrogenase with NADH, and ALT produces pyruvate, which is reduced by lactate dehydrogenase with NADH. The decrease in NADH at 340 nm is proportional to enzyme activity.

In contrast, the Reitman–Frankel method is a colorimetric assay. It forms a hydrazone with 2,4-dinitrophenylhydrazine and is measured in the visible range (around 546 nm), not UV. Therefore, UV-spectrophotometry for transaminase determination corresponds to the Karmen/AST or Walker/ALT methods, and not the colorimetric Reitman–Frankel method.