At what wavelength is the absorbance change measured when monitoring enzyme activity involving NADH?

NADH, or nicotinamide adenine dinucleotide in its reduced form, exhibits a strong absorbance peak at approximately 340 nm. This wavelength is critical in enzyme activity assays that involve NADH, as it allows for accurate monitoring of its concentration changes during enzymatic reactions. When NADH is oxidized to NAD+, the decrease in absorbance at 340 nm reflects the enzymatic activity, making this wavelength a standard choice in spectrophotometric methods involving NADH.

By measuring the absorbance at this specific wavelength, one can quantify the rate of the reaction based on the change in NADH concentration. This specific absorbance characteristic is fundamental in biochemical assays, as NADH is commonly involved in various metabolic pathways. Using a wavelength of 340 nm ensures that the assay is sensitive to even small changes in NADH concentration, providing precise activity readings of the enzyme being studied.