title: Convergent evolution of hydroxylation mechanisms in the fungal kingdom: molybdenum cofactor-independent hydroxylation of xanthine via alpha-ketoglutarate-dependent dioxygenases.
abstract: The xanthine oxidases and dehydrogenases are among the most conserved enzymes in all living kingdoms. They contain the molybdopterin cofactor Moco. We show here that in the fungi, in addition to xanthine dehydrogenase, a completely different enzyme is able to catalyse the oxidation of xanthine to uric acid. In Aspergillus nidulans this enzyme is coded by the xanA gene. We have cloned the xanA gene and determined its sequence. A deletion of the gene has the same phenotype as the previously known xanA1 miss-sense mutation. Homologues of xanA exist only in the fungal kingdom. We have inactivated the cognate gene of Schizosaccharomyces pombe and this results in strongly impaired xanthine utilization as a nitrogen source. We have shown that the Neurospora crassa homologue is functionally equivalent to xanA. The enzyme coded by xanA is an alpha-ketoglutarate- and Fe(II)-dependent dioxygenase which shares a number of properties with other enzymes of this group. This work shows that only in the fungal kingdom, an alternative mechanism of xanthine oxidation, not involving Moco, has evolved using the dioxygenase scaffold.
authors.affiliation: Institut de Génétique et de Microbiologie, Université Paris-Sud, Bâtiment 409, UMR 8621 CNRS, 91405 Orsay Cedex, France.
authors.forename: Antonietta
authors.initials: A
authors.lastname: Cultrone
authors.forename: Claudio
authors.initials: C
authors.lastname: Scazzocchio
authors.forename: Michel
authors.initials: M
authors.lastname: Rochet
authors.forename: Gabriela
authors.initials: G
authors.lastname: Montero-Morán
authors.forename: Christine
authors.initials: C
authors.lastname: Drevet
authors.forename: Rafael
authors.initials: R
authors.lastname: Fernández-Martín
mesh_terms: D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D003067:Coenzymes / Q000378:metabolism*; D018076:DNA, Complementary; D049308:Dioxygenases / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005658:Fungi / Q000235:genetics / Q000378:metabolism*; D006900:Hydroxylation; D007656:Ketoglutaric Acids / Q000378:metabolism*; D008667:Metalloproteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D000090006:Molybdenum Cofactors; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics; D011621:Pteridines / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014969:Xanthine Oxidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D003067:Coenzymes; D018076:DNA, Complementary; D049308:Dioxygenases; D005656:Fungal Proteins; D007656:Ketoglutaric Acids; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D011621:Pteridines; D014969:Xanthine Oxidase; C022261:molybdopterin; C503093:xanthine dioxygenase, Aspergillus nidulans