ALDH8A1 catalyses the NAD-dependent oxidation of 2-aminomuconic semialdehyde, a step in the kynurenine metabolic pathway of L-tryptophan degradation. The reaction converts 2-aminomuconic semialdehyde to 2-aminomuconate, which is why UniProt lists the protein as 2-aminomuconic semialdehyde dehydrogenase (EC 1.2.1.32).

The enzyme also has a role in retinoid biology. According to the NCBI Gene summary, it converts 9-cis-retinal into 9-cis-retinoic acid, a ligand of the retinoid X receptor, and shows approximately 40-fold higher activity with 9-cis-retinal than with all-trans-retinal. This places ALDH8A1 at the junction of amino acid catabolism and retinoid signalling. The protein is localised to the cytoplasm.

The ALDH8A1 gene encodes a member of the aldehyde dehydrogenase family and is listed by HGNC in the aldehyde dehydrogenases gene group. Its previous name was aldehyde dehydrogenase 8 family, member A1, and ALDH12 is a previous symbol. A mouse ortholog, Aldh8a1, is recorded. Researchers studying the ALDH8A1 protein typically use it as a reference point when comparing aldehyde dehydrogenase substrate specificity, tryptophan catabolism and retinoic acid production.