Structure and Function of D-Amino Acid Oxidase

VIII. Circular Dichroism Study in the Ultraviolet Region

Abstract

1. The circular dichroism (CD) spectra of the apo- and holoenzyme of D-amino acid oxidase [D-amino acid: O₂ oxidoreductase (deaminating), EC 1. 4. 3. 3] in the farultraviolet region were analysed by a curve-fitting technique using the data for poly-L-lysine. The results indicate that the apoenzyme contains 17% α-helix, 32% β-structure, and 51% unordered conformation, and the holoenzyme 16% α-helix, 38% β-structure, and 46% unordered conformation.
2. The CD spectrum of the holoenzyme in the near-ultraviolet region exhibits a negative band around 297nm, a sharp positive band at 289nm and a broad positive band ranging from 255 to 275nm, differing from that of the apoenzyme. The sharp positive band at 289nm seems to be ascribable to the contribution of tryptophanyl residues, suggesting that conformational change occurs in the apoenzyme upon complex formation with the coenzyme.