title: Identification and characterization of 2-keto-3-deoxy-L-rhamnonate dehydrogenase belonging to the MDR superfamily from the thermoacidophilic bacterium Sulfobacillus thermosulfidooxidans: implications to L-rhamnose metabolism in archaea.
abstract: We identified the non-phosphorylated L-rhamnose metabolic pathway (Rha_NMP) genes that are homologous to those in the thermoacidophilic archaeon Thermoplasma acidophilum in the genome of the thermoacidophilic bacterium Sulfobacillus thermosulfidooxidans. However, unlike previously known 2-keto-3-deoxy-L-rhamnonate (L-KDR) dehydrogenase (KDRDH) which belongs to the short chain dehydrogenase/reductase superfamily, the putative KDRDHs in S. thermosulfidooxidans (Sulth_3557) and T. acidophilum (Ta0749) belong to the medium chain dehydrogenase/reductase (MDR) superfamily. We demonstrated that Sulth_3559 and Sulth_3557 proteins from S. thermosulfidooxidans function as L-rhamnose dehydrogenase and KDRDH, respectively. Sulth_3557 protein is an NAD(+)-specific KDRDH with optimal temperature and pH of 50 °C and 9.5, respectively. The K m and V max values for L-KDR were 2.0 mM and 12.8 U/mg, respectively. Sulth_3557 also showed weak 2,3-butanediol dehydrogenase activity. Phylogenetic analysis suggests that Sulth_3557 and its homologs form a new subfamily in the MDR superfamily. The results shown in this study imply that thermoacidophilic archaea metabolize L-rhamnose to pyruvate and L-lactate by using the MDR-family KDRDH similarly to that of the thermoacidophilic bacterium S. thermosulfidooxidans.
authors.affiliation: Department of Chemical Engineering, Pohang University of Science and Technology, San 31, Hyoja Dong, Pohang, 790-784, Korea.
authors.forename: Jungdon
authors.initials: J
authors.lastname: Bae
authors.forename: Suk Min
authors.initials: SM
authors.lastname: Kim
authors.forename: Sun Bok
authors.initials: SB
authors.lastname: Lee
mesh_terms: D001105:Archaea / Q000201:enzymology / Q000378:metabolism*; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D056449:Bacillales / Q000201:enzymology* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002237:Carbohydrate Dehydrogenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011485:Protein Binding; D012210:Rhamnose / Q000378:metabolism*
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D002237:Carbohydrate Dehydrogenases; C022524:L-rhamnose dehydrogenase; D012210:Rhamnose