ALDH1

ALDH1 refers to the aldehyde dehydrogenase 1 family of enzymes, a group of cytosolic enzymes that catalyze the NAD+-dependent oxidation of aldehydes to their corresponding carboxylic acids. Members include ALDH1A1, ALDH1A2, and ALDH1A3, which together contribute to two major cellular roles: detoxification of reactive aldehydes generated by lipid peroxidation or alcohol metabolism, and the biosynthesis of retinoic acid from retinaldehyde, a critical signaling molecule in development and tissue homeostasis.

ALDH1A1 is widely expressed and often used as a general marker of stem and progenitor cells in multiple tissues. ALDH1A2 and ALDH1A3 encode retinaldehyde dehydrogenases (RALDH2 and RALDH3, respectively) that are particularly important for producing retinoic acid during embryogenesis and in adult tissues. The enzymes can be detected by specific activity assays, such as the ALDEFLUOR assay, which measures aldehyde dehydrogenase activity in cells.

In cancer research, high ALDH1 activity is associated with a subpopulation of cells exhibiting stem-like properties and resistance to chemotherapy in various tumor types. As such, ALDH1 enzymes are studied as biomarkers for cancer stem cells and as potential therapeutic targets, though their roles can vary by tissue type and context.

Although ALDH2, a mitochondrial aldehyde dehydrogenase involved in ethanol metabolism, is a related family member, the ALDH1 family is distinct in its cytosolic localization and substrate preferences. Overall, ALDH1 enzymes contribute to cellular defense against aldehyde stress and to retinoic acid signaling essential for development and tissue maintenance.