DAO and schizophrenia: This hypothesis is supported by the fact that the flavoprotein D-amino acid oxidase (DAO) was shown to degrade the gliotransmitter D-Ser, a potent activator of N-methyl-d-aspartate-type glutamate receptors, while a lot of evidence has suggested that DAO, together with its activator, G72 protein, may play a key role in the pathophysiology of schizophrenia.