Identification and characterization of the Tuber borchii d-mannitol dehydrogenase which defines a new subfamily within the polyol-specific medium chain dehydrogenases

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• 作者：Paola Ceccaroli ; Roberta Saltarelli ; Michele Guescini ; Emanuela Polidori ; Michele Buffalini ; Michele Menotta ; Raffaella Pierleoni ; Elena Barbieri ; Vilberto Stocchi
• 关键词：d-mannitol ; d-mannitol dehydrogenase ; MDR superfamily ; Symbiotic fungus ; Tuber borchii
• 刊名：Fungal Genetics and Biology
• 出版年：2007
• 出版时间：October 2007
• 年：2007
• 卷：44
• 期：10
• 页码：965-978
• 全文大小：514 K

文摘

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.