Characterization of Sulfolobus solfataricus 2-Keto-3-deoxy-D-gluconate Kinase in the Modified Entner-Doudoroff Pathway
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The thermoacidophilic archaeon <I>Sulfolobus solfataricus</I> is known to utilize <small>D</small>-glucose <I>via</I> the nonphosphorylated Entner-Doudoroff (ED) pathway. But, the genome database shows that this microorganism has a gene (<I>kdgK</I>) encoding 2-keto-3-deoxy-<small>D</small>-gluconate (KDG) kinase (KDGK) which phosphorylates KDG to 2-keto-3-deoxy-6-phosphogluconate. Interestingly, <I>kdgK</I> and three other genes in the modified ED pathway are organized as an operon-like structure. In this study, we report confirmation of the catalytic activity of the <I>S. solfataricus</I> KDGK protein. We also found that the <I>kdgK</I> gene was transcribed as polycistronic transcripts. Proteome analysis of cell lysate revealed that all gene products in the <I>kdgK</I> operon were expressed as functional proteins. These results strongly indicate that <I>S. solfataricus</I> metabolizes <small>D</small>-glucose <I>via</I> the 'partially' nonphosphorylated ED pathway. A purified recombinant <I>S. solfataricus</I> KDGK had <I>K</I><SUB>m</SUB> and <I>k</I><SUB>cat</SUB> values of 0.14 m<small>M</small> and 60.8 s<SUP>−1</SUP> respectively for KDG, and showed maximal activity at temperatures between 70 and 80 °C and pHs between 7.0 and 8.0.
- Agricultural and Biological Chemistry
Agricultural and Biological Chemistry 70(6), 1308-1316, 2006-06-23
Japan Society for Bioscience, Biotechnology, and Agrochemistry