D-amino-acid oxidase (DAO) is a ~39 kDa protein. Catalyzes the oxidative deamination of D-amino acids with broad substrate specificity. Required to catabolize D-amino acids synthesized endogenously, of gastrointestinal bacterial origin or obtained from the diet, and to use these as nutrients. Regulates the level of D-amino acid neurotransmitters in the brain, such as D-serine, a co-agonist of N-methyl D-aspartate (NMDA) receptors, and may modulate synaptic transmission. Catalyzes the first step of the racemization of D-DOPA to L-DOPA, for possible use in an alternative dopamine biosynthesis pathway. Also catalyzes the first step of the chiral inversion of N(gamma)-nitro-D-arginine methyl ester (D-NNA) to its L-enantiomer L-NNA that acts as a nitric oxide synthase inhibitor. 2. Kawazoe, T. et al. (2006) Protein science : a publication of the Protein Society 15, 2708-17. PMID: 170883223. Kawazoe, T. et al. (2007) Biochemical and biophysical research communications 355, 385-91. PMID: 173030724. Sacchi, S. et al. (2008) The Journal of biological chemistry 283, 22244-56. PMID: 185445345. Mitchell, J. et al. (2010) Proceedings of the National Academy of Sciences of the United States of America 107, 7556-61. PMID: 203684218. Sasabe, J. et al. (2012) Proceedings of the National Academy of Sciences of the United States of America 109, 627-32. PMID: 222039869. Caldinelli, L. et al. (2013) Biochimica et biophysica acta 1832, 400-10. PMID: 2321995410. Katane, M. et al. (2013) Journal of medicinal chemistry 56, 1894-907. PMID: 23391306 | 
