| Property | Value | |----------|-------| | Protein Name | D-Amino Acid Oxidase | | Gene | DAO/DAOA | | UniProt ID | O00327 | | Molecular Weight | ~40 kDa | | Subcellular Localization | Peroxisomes | | Protein Family | FAD-dependent oxidoreductases |
</div>
Overview
D-Amino Acid Oxidase (DAO/DAOA) is a flavin adenine dinucleotide (FAD)-dependent enzyme that catalyzes the oxidative deamination of D-amino acids[@pollegioni2007]. It has gained significant attention in neuroscience due to its proposed role in modulating [NMDA receptor](/entities/nmda-receptor) signaling and its genetic association with schizophrenia and other neuropsychiatric disorders.
Structure
DAO contains characteristic structural features essential for its enzymatic function:
FAD-binding domain: The N-terminal region (approximately 30-200 amino acids) contains the binding site for the flavin adenine dinucleotide cofactor. This domain adopts a characteristic Rossmann-like fold that stabilizes the FAD molecule through hydrogen bonds and hydrophobic interactions[@pawlowski2001].
Active site: The central region forms the substrate-binding pocket that recognizes the D-stereoisomer of amino acids. The active site contains key catalytic residues including a conserved serine, tyrosine, and glutamate that participate in the oxidative deamination reaction.
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D-Amino Acid Oxidase (DAO/DAOA) Protein
<div class="infobox infobox-protein">
| Property | Value | |----------|-------| | Protein Name | D-Amino Acid Oxidase | | Gene | DAO/DAOA | | UniProt ID | O00327 | | Molecular Weight | ~40 kDa | | Subcellular Localization | Peroxisomes | | Protein Family | FAD-dependent oxidoreductases |
</div>
Overview
D-Amino Acid Oxidase (DAO/DAOA) is a flavin adenine dinucleotide (FAD)-dependent enzyme that catalyzes the oxidative deamination of D-amino acids[@pollegioni2007]. It has gained significant attention in neuroscience due to its proposed role in modulating [NMDA receptor](/entities/nmda-receptor) signaling and its genetic association with schizophrenia and other neuropsychiatric disorders.
Structure
DAO contains characteristic structural features essential for its enzymatic function:
FAD-binding domain: The N-terminal region (approximately 30-200 amino acids) contains the binding site for the flavin adenine dinucleotide cofactor. This domain adopts a characteristic Rossmann-like fold that stabilizes the FAD molecule through hydrogen bonds and hydrophobic interactions[@pawlowski2001].
Active site: The central region forms the substrate-binding pocket that recognizes the D-stereoisomer of amino acids. The active site contains key catalytic residues including a conserved serine, tyrosine, and glutamate that participate in the oxidative deamination reaction.
Peroxisomal targeting signal: The C-terminal region contains the tripeptide SKL (serine-lysine-leucine) peroxisomal targeting signal (PTS1), which directs the enzyme to peroxisomes.
Dimerization interface: DAO forms functional homodimers, with each monomer capable of independently binding FAD and substrate.
Enzyme Catalysis
Reaction Mechanism
DAO catalyzes the oxidative deamination of D-amino acids:
D-amino acid + O2 + H2O → 2-oxo acid + NH3 + H2O2
The reaction proceeds through a reductive half-reaction where the substrate reduces the flavin, followed by an oxidative half-reaction where the reduced flavin is reoxidized by molecular oxygen, producing hydrogen peroxide as a byproduct.
Substrate Specificity
DAO shows broad specificity for D-amino acids:
D-serine: Primary physiological substrate in the brain
D-alanine: Significant substrate in peripheral tissues
D-aspartate: Important in endocrine tissues
D-phenylalanine: Metabolized at lower rates
Normal Function
D-Amino Acid Metabolism
DAO plays a crucial role in D-amino acid catabolism:
D-serine regulation: As the primary catabolic enzyme for D-serine, DAO tightly controls the levels of this important neuromodulator
Renal metabolism: DAO in kidneys metabolizes D-amino acids from diet and protein turnover
Liver function: Hepatic DAO processes circulating D-amino acids
Neurotransmission Modulation
In the central nervous system, DAO modulates neurotransmission through:
D-serine regulation: D-serine is a major NMDA receptor co-agonist, and DAO controls its extracellular levels
Glutamatergic signaling: By regulating D-serine, DAO indirectly modulates NMDA receptor activity
Synaptic plasticity: NMDA receptor activation is critical for [long-term potentiation](/mechanisms/long-term-potentiation) and memory formation
Excitotoxicity: Excessive D-serine may contribute to excitotoxic neuronal damage
Role in Disease
Schizophrenia
DAO/DAOA is one of the most extensively studied schizophrenia risk genes[@lin2014][@rogaeva2007]:
Genetic association: Multiple genome-wide association studies (GWAS) have identified DAO/DAOA variants as significant risk factors for schizophrenia
Haplotype structure: Specific haplotypes spanning the DAO gene show association with disease risk
Expression studies: Post-mortem brain studies reveal altered DAO expression in prefrontal [cortex](/brain-regions/cortex) of schizophrenia patients
Endophenotypes: DAO variants may influence specific cognitive and neurobiological endophenotypes
Amyotrophic Lateral Sclerosis
D-serine accumulation: Altered DAO activity may contribute to excitotoxicity in ALS
Motor neuron vulnerability: May affect susceptibility of motor [neurons](/entities/neurons) to excitotoxic damage
Epilepsy
Seizure susceptibility: DAO activity may influence seizure threshold
Therapeutic implications: DAO modulators may have anticonvulsant properties
Therapeutic Implications
DAO Inhibitors
Several DAO inhibitors have been developed as potential therapeutics:
4-Phenylbutyric acid (PBA): Weak DAO inhibitor
Compound 6: Potent DAO inhibitor with central activity
FAD analogs: Modified flavins that inhibit DAO
D-Serine-Based Approaches
D-serine supplementation: May benefit patients with impaired DAO function
Glycine site modulators: Target the NMDA receptor glycine site
Key Publications
[Pollegioni, L. & Piubelli, L. (2007) D-amino acid oxidase: physiological role and applications (FEBS Journal)](https://doi.org/10.1111/j.1742-4658.2007.05932.x)
[Bendikov, I. et al. (2005) D-Serine and schizophrenia (Biochimica et Biophysica Acta)](https://doi.org/10.1016/j.bbapap.2005.06.010)
[Miyoshi, K. et al. (2010) DAO and schizophrenia (Human Molecular Genetics)](https://doi.org/10.1093/hmg/ddq311)
Cross-References
[DAOA Gene](/genes/daoa) — Gene encoding DAO
[Schizophrenia](/diseases/schizophrenia) — Primary disease association
[NMDA Receptor](/mechanisms/nmda-receptor-signaling) — Related mechanism
See Also
[tau-protein](/proteins/tau) — Related [tau](/proteins/tau) kinase substrate in AD
[amyloid-beta](/proteins/amyloid-beta-protein) — Related [APP](/entities/app-protein) cleavage product
[GSK3B](/proteins/gsk3b) — Major kinase in neurodegeneration
[CDK5](/genes/cdk5) — Another tau kinase
[BACE1](/entities/bace1) — Beta-secretase in amyloidogenesis
External Links
[UniProt](https://www.uniprot.org/) - Protein sequence and functional data
[PubMed](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
[PDB](https://www.rcsb.org/) - Protein structure data
References
Unknown, Pollegioni, L. & Piubelli, L. (2007). D-amino acid oxidase: physiological role and applications. FEBS Journal, 274(S1), 2630 (2007)
Pawlowski, M. et al., (2001). The crystal structure of D-amino acid oxidase at very high resolution. Journal of Molecular Biology, 307(1), 171-188 (2001)
Lin, C.H. et al., (2014). D-amino acid oxidase and schizophrenia. Current Medicinal Chemistry, 21(12), 1344-1359 (2014)
Unknown, Rogaeva, E. & St George-Hyslop, P.H. (2007). Genetic evidence for a novel susceptibility gene for schizophrenia. Nature Genetics, 39(2), 139-140 (2007)