Properties of D‐amino‐acid oxidase from Rhodotorula gracilis

Abstract

The flavoprotein D‐amino‐acid oxidase was purified to homogeneity from the yeast Rhodotorula gracilis by a highly reproducible procedure. The amino acid composition of the protein was determined; the protein monomer had a molecular mass of 39 kDa and contained one molecule of FAD. The ratio between A274/A455 was about 8.2. D‐Amino‐acid oxidase from yeast showed typical flavin spectral perturbations on binding of the competitive inhibitor benzoate and was reduced by D‐alanine under anaerobiosis. The enzyme reacted readily with sulfite to form a covalent reversible adduct and stabilized the red anionic form of the flavin semiquinone on photoreduction in the presence of 5‐deazariboflavin; the 3,4‐dihydro‐FAD from was not detectable after reduction with sodium borohydride. Thus D‐amino‐acid oxidase from yeast exhibited most of the general properties of the dehydrogenase/oxidase class of flavoproteins; at the same time, the enzyme showed some peculiar features with respect to the same protein from pig kidney. Copyright © 1989, Wiley Blackwell. All rights reserved