PMID:1650346
| Citation |
Badia, J, Gimenez, R, Baldomá, L, Barnes, E, Fessner, WD and Aguilar, J (1991) L-lyxose metabolism employs the L-rhamnose pathway in mutant cells of Escherichia coli adapted to grow on L-lyxose. J. Bacteriol. 173:5144-50 |
|---|---|
| Abstract |
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. |
| Links | |
| Keywords |
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/secretion; Kinetics; Membrane Transport Proteins/metabolism; Mutation/physiology; Pentoses/metabolism; Phosphotransferases/metabolism; Phosphotransferases (Alcohol Group Acceptor); Rhamnose/metabolism; Symporters |
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