D-Amino acid oxidase (EC 1.4.3.3) forms an inhibited complex with the nucleotide- and aromatic-binding-site affinity reagent 9-azido[3H]acridine. Tryptic digestion of the photolysed complex yielded two radioactive peptides, 222-265 (T23) and 298-328 (T29), which core and secondary structure analysis revealed to be exposed, but which also comprised the propargylglycine-binding residues. This suggests that at least parts of the peptides containing these residues are in the active centre and that they are spatially close to the flavin-binding site.
