The active site of murine aldehyde oxidase 3 (PDB 3ZYV). Conserved residues with the bovine xanthine oxidase include Phe 914/919 (bovine/murine numbering), Phe 1009/1014, Glu 1261/1266, and Gln 767/772. Amino acid residues that are not conserved include Glu 802/Ala 807, Arg 880/Tyr 885 (a methionine in most other aldehyde oxidases), His 884/Lys 889, and Leu 1014/Tyr 1019. Compare with Figure 22.