title: Identification and characterization of the Tuber borchii D-mannitol dehydrogenase which defines a new subfamily within the polyol-specific medium chain dehydrogenases.
abstract: A novel NADP(+)-dependent D-mannitol dehydrogenase and the corresponding gene from the plant symbiotic ascomycete fungus Tuber borchii was identified and characterized. The enzyme, called TbMDH, is a homotetramer with two zinc atoms per subunit. It catalyzed both D-fructose reduction and D-mannitol oxidation, although it showed the highest substrate specificity and catalytic efficiency for D-fructose. Co-factor specificity was restricted to NADP(H) and the reaction proceeded via a sequential ordered Bi Bi mechanism. The carbon responsive transcriptional pattern showed that Tbmdh is up-regulated when mycelia are transferred to a culture medium containing D-mannitol or D-fructose. The phylogenetic analysis showed TbMDH to be the first example of a fungal D-mannitol-2-dehydrogenase belonging to the medium-chain dehydrogenase/reductases (MDRs). The enzyme identified a new group of proteins, most of them annotated in databases as hypothetical zinc-dependent dehydrogenases, forming a distinct subfamily among the polyol dehydrogenase family.
authors.affiliation: Istituto di Chimica Biologica Giorgio Fornaini, Università degli Studi di Urbino Carlo Bo, Via A Saffi 2, 61029, Urbino (PU), Italy. p.ceccaroli@uniurb.it
authors.forename: Paola
authors.initials: P
authors.lastname: Ceccaroli
authors.forename: Roberta
authors.initials: R
authors.lastname: Saltarelli
authors.forename: Michele
authors.initials: M
authors.lastname: Guescini
authors.forename: Emanuela
authors.initials: E
authors.lastname: Polidori
authors.forename: Michele
authors.initials: M
authors.lastname: Buffalini
authors.forename: Michele
authors.initials: M
authors.lastname: Menotta
authors.forename: Raffaella
authors.initials: R
authors.lastname: Pierleoni
authors.forename: Elena
authors.initials: E
authors.lastname: Barbieri
authors.forename: Vilberto
authors.initials: V
authors.lastname: Stocchi
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D007064:L-Iditol 2-Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D008354:Mannitol Dehydrogenases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D009249:NADP / Q000378:metabolism; D010802:Phylogeny
chemical_list: D009249:NADP; D008354:Mannitol Dehydrogenases; D007064:L-Iditol 2-Dehydrogenase