The assay links aldehyde processing to cofactor conversion. ALDH oxidizes the supplied aldehyde substrate into a carboxylic acid while NAD+ or NADP+ is reduced to NADH or NADPH. Because this reaction changes the measurable properties of the reaction mixture, the resulting absorbance or fluorescence signal provides an indication of ALDH activity.
NAD+ and NADP+ serve as the electron-accepting cofactors coupled to aldehyde oxidation. Their reduction to NADH or NADPH creates the signal used for quantification, so the selected cofactor determines which reaction product is monitored. This coupling allows ALDH function to be assessed through a measurable biochemical change rather than by observing aldehyde disappearance alone.
An activity measurement evaluates whether ALDH is functionally processing aldehydes, not merely whether the enzyme or its associated cellular capacity is present. The result can reflect cellular metabolism, detoxification, and responses to toxic aldehydes. It can therefore reveal metabolic alterations associated with disease that a presence-based measurement may not capture.
A typical workflow combines an aldehyde substrate with the relevant biological sample and NAD+ or NADP+. The reaction proceeds as ALDH converts the substrate and reduces the cofactor. Researchers then monitor the resulting absorbance or fluorescence change and quantify the signal to evaluate enzyme function under the selected assay conditions.
ALDH participates in aldehyde detoxification, making its measured activity relevant to liver-related investigations and cellular exposure studies. Comparing activity across samples can help indicate differences in detoxification capacity or responses to toxic aldehydes. The resulting data support evaluation of how cellular metabolism changes under disease-associated or chemically stressful conditions.
In cancer studies, ALDH measurements can help distinguish cell populations with stem-like properties from other tumor cells. Researchers can also compare activity during treatment experiments to assess metabolic responses and treatment effects. These findings support disease characterization and the development or evaluation of therapeutic strategies directed at biologically distinct cancer cell populations.