Publications

• Novel modified version of nonphosphorylated sugar metabolism--an alternative L-rhamnose pathway of Sphingomonas sp.

  Watanabe S., Makino K.

  Several bacteria, including Azotobacter vinelandii, possess an alternative pathway of L-rhamnose metabolism, which is different from the known bacterial pathway. In a previous article, a gene cluster related to this pathway was identified, consisting of the genes encoding the four metabolic enzyme ... >> More

  Several bacteria, including Azotobacter vinelandii, possess an alternative pathway of L-rhamnose metabolism, which is different from the known bacterial pathway. In a previous article, a gene cluster related to this pathway was identified, consisting of the genes encoding the four metabolic enzymes L-rhamnose-1-dehydrogenase (LRA1), L-rhamnono-gamma-lactonase (LRA2), L-rhamnonate dehydratase (LRA3) and L-2-keto-3-deoxyrhamnonate (L-KDR) aldolase (LRA4), by which L-rhamnose is converted into pyruvate and L-lactaldehyde, through analogous reaction steps to the well-known Entner-Doudoroff (ED) pathway. In this study, bioinformatic analysis revealed that Sphingomonas sp. possesses a gene cluster consisting of LRA1-3 and two genes of unknown function, LRA5 and LRA6. LRA5 catalyzed the NAD(+)-dependent dehydrogenation of several L-2-keto-3-deoxyacid-sugars, including L-KDR. Furthermore, the reaction product was converted to pyruvate and L-lactate by LRA6; this is different from the pathway of Azotobacter vinelandii. Therefore, LRA5 and LRA6 were assigned as the novel enzymes L-KDR 4-dehydrogenase and L-2,4-diketo-3-deoxyrhamnonate hydrolase, respectively. Interestingly, both enzymes were phylogenetically similar to L-rhamnose-1-dehydrogenase and D-2-keto-3-deoxyarabinonate dehydratase, respectively, and the latter was involved in the archeal nonphosphorylative d-arabinose pathway, which is partially analogous to the ED pathway. The introduction of LRA1-4 or LRA1-3, LRA5 and LAR6 compensated for the L-rhamnose-defective phenotype of an Escherichia coli mutant. Metabolic evolution and promiscuity between the alternative l-rhamnose pathway and other sugar pathways analogous to the ED pathway are discussed. << Less

  FEBS J. 276:1554-1567(2009) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• 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.

  Bae J., Kim S.M., Lee S.B.

  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-d ... >> More

  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. << Less

  Extremophiles 19:469-478(2015) [PubMed] [EuropePMC]