ALDH8A1 catalyzes the NAD+-dependent oxidation of 2-aminomuconic semialdehyde (2-AMS) in the kynurenine pathway of L-tryptophan degradation 1. Previously annotated as a retinal dehydrogenase based on substrate preferences, ALDH8A1 has been reassigned to this metabolic pathway with catalytic efficiency equivalent to bacterial AMSDH 1. The enzyme also participates in retinoic acid synthesis from retinaldehyde, contributing to cellular differentiation and tumor suppression 2. ALDH8A1 expression is epigenetically regulated by microRNA hsa-miR-1301-3p, which suppresses its expression in liver cells and blocks ethanol-induced induction 3. The gene is dysregulated in hepatocellular carcinoma as part of a four-gene signature (ALDH2, ALDH5A1, ALDH6A1, ALDH8A1) predicting poor prognosis and immunosuppressive features 4. ALDH8A1 dysregulation has also been implicated in amyotrophic lateral sclerosis pathology and aflatoxin B1-induced hepatotoxicity 56. As a member of the broader ALDH superfamily, ALDH8A1 represents a potential biomarker for identifying cancer stem cells and a therapeutic target in malignant diseases 7. Its dual roles in both tryptophan catabolism and retinoid metabolism position it at the intersection of immunoregulation and cellular differentiation.