Flavoprotein oxidase product released

DAAO is one of the most extensively studied flavoprotein oxidases. The homodimeric enzyme catalyzes the strictly stere-ospecihc oxidative deamination of neutral and hydrophobic D-amino acids to give a-keto acids and ammonia (Fig. 3a). In the reductive half-reaction the D-amino acid substrate is converted to the imino acid product via hydride transfer (21). During the oxidative half-reaction, the imino acid is released and hydrolyzed. Mammalian and yeast DAAO share the same catalytic mechanism, but they differ in kinetic mechanism, catalytic efficiency, substrate specificity, and protein stability. The dimeric structures of the mammalian enzymes show a head-to-head mode of monomer-monomer interaction, which is different from the head-to-tail mode of dimerization observed in Rhodotorula gracilis DAAO (20). Benzoate is a potent competitive inhibitor of mammalian DAAO. Binding of this ligand strengthens the apoenzyme-flavin interaction and increases the conformational stability of the porcine enzyme. 

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