title: Crystal structure of Pseudomonas fluorescens mannitol 2-dehydrogenase: evidence for a very divergent long-chain dehydrogenase family.
abstract: Mannitol 2-dehydrogenase from Pseudomonas fluorescens (pfMDH) is a secondary alcohol dehydrogenase that catalyzes the reversible NAD(P)-dependent oxidation of D-mannitol to D-fructose, D-arabinitol to D-xylulose, and D-sorbitol to L-sorbose. It is a member of the mostly prokaryotic family of long-chain mannitol dehydrogenases that so far includes 66 members. Unlike other alcohol and polyol dehydrogenases that utilize metal cofactors or a conserved active-site tyrosine for catalysis, an invariant lysine is the general base. The crystal structure of pfMDH in a binary complex with NAD(H) and a ternary complex with NAD(H) and D-mannitol have been determined to 1.7 and 1.8 A resolution respectively. Comparison of secondary structure assignment to sequence alignments suggest the shortest members of this family, mannitol-1-phosphate 5-dehydrogenases, retain core elements but lack secondary structural components found on the surface of pfMDH. The elements predicted to be absent are distributed throughout the primary sequence, implying that a simple truncation or fusion did not occur. The closest structural neighbors are 6-phosphogluconate dehydrogenase, UDP-glucose dehydrogenase, N-(1-D-carboxyethyl)-L-norvaline dehydrogenase, and glycerol-3-phosphate dehydrogenase. Although sequence identity is only a barely recognizable 7-10%, conservation of secondary structural elements as well as homologous residues that are contributed to the active site indicates they may be related by divergent evolution.
authors.affiliation: Section of Molecular and Cellular Biology, University of California, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Kavanagh
authors.forename: Mario
authors.initials: M
authors.lastname: Klimacek
authors.forename: Bernd
authors.initials: B
authors.lastname: Nidetzky
authors.forename: David K
authors.initials: DK
authors.lastname: Wilson
mesh_terms: D018360:Crystallography, X-Ray; D008354:Mannitol Dehydrogenases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D011551:Pseudomonas fluorescens / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D008354:Mannitol Dehydrogenases