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

Extremophiles. 2015 Mar;19(2):469-78. doi: 10.1007/s00792-015-0731-8. Epub 2015 Jan 24.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Archaea / enzymology
  • Archaea / metabolism*
  • Archaeal Proteins / chemistry
  • Archaeal Proteins / genetics
  • Archaeal Proteins / metabolism
  • Bacillales / enzymology*
  • Bacillales / metabolism
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Carbohydrate Dehydrogenases / chemistry
  • Carbohydrate Dehydrogenases / genetics
  • Carbohydrate Dehydrogenases / metabolism*
  • Phylogeny
  • Protein Binding
  • Rhamnose / metabolism*


  • Archaeal Proteins
  • Bacterial Proteins
  • Carbohydrate Dehydrogenases
  • L-rhamnose dehydrogenase
  • Rhamnose