title: L-Sorbose metabolism in Klebsiella pneumoniae and Sor+ derivatives of Escherichia coli K-12 and chemotaxis toward sorbose.
abstract: L-Sorbose degradation in Klebsiella pneumoniae was shown to follow the pathway L-sorbose leads to L-sorbose-1-phosphate leads to D-glucitol-6-phosphate leads to D-fructose-6-phosphate. Transport and phosphorylation of L-sorbose was catalyzed by membrane-bound enzyme IIsor of the phosphoenolpyruvate-dependent carbohydrate:phosphotransferase system, specific for and regulated by this ketose and different from all other enzymes II described thus far. Two soluble enzymes, an L-sorbose-1-phosphate reductase and a D-glucitol-6-phosphate dehydrogenase, were involved in the conversion of L-sorbose-1-phosphate to D-fructose-6-phosphate. This dehydrogenase was temperature sensitive, preventing growth of wild-type strains of K. pneumoniae at temperatures above 35 degrees C in the presence of L-sorbose. The enzyme was distinct from a second D-glucitol-6-phosphate dehydrogenase involved in the metabolism of D-glucitol. The sor genes were transferred from the chromosome of nonmotile strains of K. pneumoniae by means of a new R'sor+ plasmid to motile strains of Escherichia coli K-12. Such derivatives not only showed the temperature-sensitive Sor+ phenotype characteristic for K. pneumoniae or Sor+ wild-type strains of E. coli, but also reacted positively to sorbose in chemotaxis tests.
mesh_terms: D001692:Biological Transport; D002384:Catalysis; D002633:Chemotaxis / Q000187:drug effects*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005798:Genes, Bacterial; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics; D010641:Phenotype; D010766:Phosphorylation; D010957:Plasmids; D013013:Sorbose / Q000235:genetics / Q000378:metabolism*
chemical_list: D013013:Sorbose