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Induction of the galactose enzymes in Escherichia coli is independent of the C-1-hydroxyl optical configuration of the inducer D-galactose
- Source :
- Journal of bacteriology. 190(24)
- Publication Year :
- 2008
-
Abstract
- The two optical forms of aldohexose galactose differing at the C-1 position, α- d -galactose and β- d -galactose, are widespread in nature. The two anomers also occur in di- and polysaccharides, as well as in glycoconjugates. The anomeric form of d -galactose, when present in complex carbohydrates, e.g., cell wall, glycoproteins, and glycolipids, is specific. Their interconversion occurs as monomers and is effected by the enzyme mutarotase (aldose-1-epimerase). Mutarotase and other d -galactose-metabolizing enzymes are coded by genes that constitute an operon in Escherichia coli . The operon is repressed by the repressor GalR and induced by d -galactose. Since, depending on the carbon source during growth, the cell can make only one of the two anomers of d -galactose, the cell must also convert one anomer to the other for use in specific biosynthetic pathways. Thus, it is imperative that induction of the gal operon, specifically the mutarotase, be achievable by either anomer of d -galactose. Here we report in vivo and in vitro experiments showing that both α- d -galactose and β- d -galactose are capable of inducing transcription of the gal operon with equal efficiency and kinetics. Whereas all substitutions at the C-1 position in the α configuration inactivate the induction capacity of the sugar, the effect of substitutions in the β configuration varies depending upon the nature of the substitution; methyl and phenyl derivatives induce weakly, but the glucosyl derivative does not.
- Subjects :
- Anomer
Transcription, Genetic
Operon
Glycoconjugate
Physiology and Metabolism
Molecular Sequence Data
Repressor
Biology
medicine.disease_cause
Microbiology
chemistry.chemical_compound
medicine
Escherichia coli
gal operon
Inducer
Promoter Regions, Genetic
Molecular Biology
chemistry.chemical_classification
Base Sequence
Escherichia coli Proteins
Galactose
Gene Expression Regulation, Bacterial
chemistry
Biochemistry
Genes, Bacterial
Carbohydrate Epimerases
Plasmids
Subjects
Details
- ISSN :
- 10985530
- Volume :
- 190
- Issue :
- 24
- Database :
- OpenAIRE
- Journal :
- Journal of bacteriology
- Accession number :
- edsair.doi.dedup.....16cf96604340e5dfad605dc2e8d90f07