A New Method of Preparation of D-Amino Acid Oxidase Apoprotein and a Conformational Change after Its Combination with Flavin Adenine Dinucleotide

Abstract

Abstract The apoprotein of D-amino acid oxidase has been prepared by a new method involving dialysis of the holoenzyme against 1 M potassium bromide. The apoprotein prepared in this way has been found to have the same properties as that prepared by the classical acid-ammonium sulfate method. The effect of mixing apoprotein with flavin adenine dinucleotide has been followed by changes in absorbance at 493 mµ, by changes in flavin fluorescence and protein fluorescence, and by measuring catalytic activity. It is found that the reaction proceeds in two stages, a rapid binding of FAD being followed by slow secondary changes which correlate with the appearance of catalytic activity. Evidence is presented that the slow change is due to a change in protein conformation. Some speculation is made on the significance of this finding to the current theories of protein synthesis.