DAAO is a peroxisomal enzyme which uses FAD（flavin adenine dinucleotide) as a cofactor and oxidizes D-amino acids to the corresponding amino acids， producing ammonia and hydrogen peroxide. DAAO substrates include an extensive array of D-amino acids， but it is inactive on the naturally occurring L-amino acids. DAAO acts on a variety of D-amino acids especially on those having small hydrophobic side chains followed by those bearing polar， aromatic， and basic groups； however it doesn’t act on acidic amino acids. DAAO may be involved in acid base balance in the kidney or it could act as a detoxifying agent which removes D-amino acids accumulated during aging. DAAO regulates the neuromodulator D-serine level in the brain. DAAO is highly active towards D-DOPA and contributes to dopamine synthesis. Creatinine inhibits the DAAO in uremia. DAAO may also have a role in the pathophysiology of schizophrenia， but not in bipolar disorder.
