L-lyxose metabolism employs the L-rhamnose pathway in mutant cells of Escherichia coli adapted to grow on L-lyxose.
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.
Badia
J
J
Department of Organic Chemistry and Biochemistry, University of Freiburg, Federal Republic of Germany.
Gimenez
R
R
Baldomá
L
L
Barnes
E
E
Fessner
W D
WD
Aguilar
J
J
D000079:Acetaldehyde / Q000031:analogs & derivatives / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000378:metabolism; D000446:Aldehyde-Lyases / Q000378:metabolism; D019747:Aldose-Ketose Isomerases; D002238:Carbohydrate Epimerases / Q000378:metabolism; D002845:Chromatography; D004099:Dihydroxyacetone Phosphate / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D007661:Ketoses / Q000378:metabolism; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000378:metabolism; D009154:Mutation / Q000502:physiology; D010429:Pentoses / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor); D012210:Rhamnose / Q000378:metabolism*; D027981:Symporters
D029968:Escherichia coli Proteins; D007661:Ketoses; D026901:Membrane Transport Proteins; D010429:Pentoses; C067370:RhaT protein, E coli; D027981:Symporters; D004099:Dihydroxyacetone Phosphate; C043333:lyxose; D000445:Aldehyde Oxidoreductases; C021493:lactaldehyde dehydrogenase; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C062877:rhamnulokinase; D000446:Aldehyde-Lyases; C022526:rhamnulose-1-phosphate adolase; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; C062878:L-rhamnose isomerase; D000079:Acetaldehyde; D012210:Rhamnose; C010972:glycolaldehyde