X-ray Crystal Structure and EPR Spectra of “Arsenite-Inhibited” <i>Desulfovibrio </i><i>g</i><i>igas</i> Aldehyde Dehydrogenase: A Member of the Xanthine Oxidase Family

X-ray crystallography has been used to determine the structure of arsenite-inhibited aldehyde dehydrogenase from Desulfovibrio gigas, a member of the xanthine oxidase family of mononuclear molybdenum enzymes. The structure shows an AsO3 moiety bound to the molybdenum atom of the active site through one of the oxygen atoms. A reduced sample of arsenite-inhibited aldehyde dehydrogenase has a Mo(V) signal that shows anisotropic hyperfine and quadrupole coupling to one arsenic atom. This signal has a strong resemblance with a previously reported signal for arsenite-inhibited xanthine oxidase.