Inhibition of recombinant D-amino acid oxidase from Trigonopsis variabilis (TvDAAO) activity in the presence of different sodium salts and potassium chloride is reported. A competitive inhibition pattern by sodium chloride was observed, and an inhibition constant value of K(i) = 85 mM was calculated. Direct connection of NaCl inhibition with FAD cofactor dissociation was confirmed by measuring the fluorescence of tryptophanyl residues of the holoenzyme.