title: A novel pathway for fungal D-glucuronate catabolism contains an L-idonate forming 2-keto-L-gulonate reductase.
abstract: For the catabolism of D-glucuronate, different pathways are used by different life forms. The pathways in bacteria and animals are established, however, a fungal pathway has not been described. In this communication, we describe an enzyme that is essential for D-glucuronate catabolism in the filamentous fungus Aspergillus niger. The enzyme has an NADH dependent 2-keto-L-gulonate reductase activity forming L-idonate. The deletion of the corresponding gene, the gluC, results in a phenotype of no growth on D-glucuronate. The open reading frame of the A. niger 2-keto-L-gulonate reductase was expressed as an active protein in the yeast Saccharomyces cerevisiae. A histidine tagged protein was purified and it was demonstrated that the enzyme converts 2-keto-L-gulonate to L-idonate and, in the reverse direction, L-idonate to 2-keto-L-gulonate using the NAD(H) as cofactors. Such an L-idonate forming 2-keto-L-gulonate dehydrogenase has not been described previously. In addition, the finding indicates that the catabolic D-glucuronate pathway in A. niger differs fundamentally from the other known D-glucuronate pathways.
authors.affiliation: VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044-VTT, Finland.
authors.forename: Joosu
authors.initials: J
authors.lastname: Kuivanen
authors.affiliation: Departamento de Engenharia Química e Engenharia de Alimentos, Universidade Federal de Santa Catarina, Cx.P. 476 Centro Tecnológico, Florianópolis 88040-900, Santa Catarina, Brazil.
authors.forename: Maura H
authors.initials: MH
authors.lastname: Sugai-Guérios
authors.affiliation: VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044-VTT, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Arvas
authors.affiliation: VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044-VTT, Finland.
authors.forename: Peter
authors.initials: P
authors.lastname: Richard
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics; D002237:Carbohydrate Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005965:Glucuronates / Q000737:chemistry / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D012441:Saccharomyces cerevisiae; D013237:Stereoisomerism; D013400:Sugar Acids / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D005965:Glucuronates; D013400:Sugar Acids; C113317:idonic acid; C015252:gulonic acid; D002237:Carbohydrate Dehydrogenases