L-lyxose metabolism employs the L-rhamnose pathway in mutant cells of Escherichia coli adapted to grow on L-lyxose

J Bacteriol. 1991 Aug;173(16):5144-50. doi: 10.1128/jb.173.16.5144-5150.1991.


Escherichia coli cannot grow on L-lyxose, a pentose analog of the 6-deoxyhexose L-rhamnose, which supports the growth of this and other enteric bacteria. L-Rhamnose is metabolized in E. coli by a system that consists of a rhamnose permease, rhamnose isomerase, rhamnulose kinase, and rhamnulose-1-phosphate aldolase, which yields the degradation products dihydroxyacetone phosphate and L-lactaldehyde. This aldehyde is oxidized to L-lactate by lactaldehyde dehydrogenase. All enzymes of the rhamnose system were found to be inducible not only by L-rhamnose but also by L-lyxose. L-Lyxose competed with L-rhamnose for the rhamnose transport system, and purified rhamnose isomerase catalyzed the conversion of L-lyxose into L-xylulose. However, rhamnulose kinase did not phosphorylate L-xylulose sufficiently to support the growth of wild-type E. coli on L-lyxose. Mutants able to grow on L-lyxose were analyzed and found to have a mutated rhamnulose kinase which phosphorylated L-xylulose as efficiently as the wild-type enzyme phosphorylated L-rhamnulose. Thus, the mutated kinase, mapped in the rha locus, enabled the growth of the mutant cells on L-lyxose. The glycolaldehyde generated in the cleavage of L-xylulose 1-phosphate by the rhamnulose-1-phosphate aldolase was oxidized by lactaldehyde dehydrogenase to glycolate, a compound normally utilized by E. coli.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetaldehyde / analogs & derivatives
  • Acetaldehyde / metabolism
  • Aldehyde Oxidoreductases / metabolism
  • Aldehyde-Lyases / metabolism
  • Aldose-Ketose Isomerases*
  • Carbohydrate Epimerases / metabolism
  • Chromatography
  • Dihydroxyacetone Phosphate / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial / physiology
  • Ketoses / metabolism
  • Kinetics
  • Membrane Transport Proteins / metabolism
  • Mutation / physiology
  • Pentoses / metabolism*
  • Phosphotransferases (Alcohol Group Acceptor)*
  • Phosphotransferases / metabolism
  • Rhamnose / metabolism*
  • Symporters*


  • Escherichia coli Proteins
  • Ketoses
  • Membrane Transport Proteins
  • Pentoses
  • RhaT protein, E coli
  • Symporters
  • Dihydroxyacetone Phosphate
  • lyxose
  • Aldehyde Oxidoreductases
  • lactaldehyde dehydrogenase
  • Phosphotransferases
  • Phosphotransferases (Alcohol Group Acceptor)
  • rhamnulokinase
  • Aldehyde-Lyases
  • rhamnulose-1-phosphate adolase
  • Carbohydrate Epimerases
  • Aldose-Ketose Isomerases
  • L-rhamnose isomerase
  • Acetaldehyde
  • Rhamnose
  • glycolaldehyde