RESUMO
OBJECTIVE: We investigated the structure model and function of xylitol dehydrogenase from Aspergillus oryzae. METHODS: Xylitol dehydrogenase (XDH) gene from Aspergillus oryzae was cloned and sequenced. We constructed four tertiary structure models of XDH by homology modeling with Swiss-MODEL and Modeller and obtained the best quality model by evaluation of PROCHECK and Prosa2003. The dockings of NAD+, Zn2+ and xylitol with XDH were performed by Molsoft program. RESULTS: Structure analysis suggested that XDH was a member of medium-chain dehydrogenase/reductase (MDR) family. This was supported by the presence of the zinc-containing alcohol dehydrogenase signature and a typical alcohol dehydrogenase Rossmann fold pattern composed by NAD+ binding domain present in MDR superfamily. The molecular docking indicated that amino acid residues Asp206, Arg211, Ser255, Ser301 and Arg303 in XDH binding domain had hydrogen bonding with NAD+, His72 and Glu73 in catalytic domain had hydrogen bonding with Zn2+, Ile46, Ile349, Lys350 and Thr351 in catalytic domain had hydrogen bonding with xylitol. CONCLUSION: These key amino acid residues might play a vital role in the XDH catalytic reaction and can instruct the further directed modification of XDH.
