Crystallization of the Complex of _D-Amino-Acid Oxidase and Benzoate

Abstract

WE have been, investigating D-amino-acid oxidase apo-protein, flavin adenine dinucleotide and the substrate with reference to complex formation^1,2. In the previous communication¹, it was reported that the addition of the apo-protein to flavin adenine dinucleotide causes a shift and decrease of the absorption peak at 450 mµ of the latter. It was also found that the co-existence of benzoate, a substrate-substitute, and the apo-protein causes further marked changes in the absorption spectrum of the flavin, adenine dinucleotide. Two important changes were especially noted : (1) the intensity of the absorption at 450 mµ is further decreased and that at 485 mµ is increased to form a shoulder, and (2) a new absorption peak appears at 465 mµ. These results indicate that both the apo-protein and the benzoate combine with two different binding sites of the isoalloxazine nucleus of flavin adenine dinucleotide. On the other hand, the fact that benzoate competes with the substrate, D-amino-acid^3,4, indicates combination between benzoate and the apo-protein. Hence it may be considered that the apo-protein, flavin adenine dinucleotide and benzoate combine to form a tight complex⁵.