Utilization of exogenous glucose-1-phosphate as a source of carbon or phosphate by Escherichia coli K12: respective roles of acid glucose-1-phosphatase, hexose-phosphate permease, phosphoglucomutase and alkaline phosphatase.
The periplasmic acid glucose-1-phosphatase (G-1-Pase) encoded by gene agp is necessary for the growth of Escherichia coli in a minimal medium containing glucose-1-phosphate (G-1-P) as the sole source of carbon. From a mutant in which the agp gene was inactivated, suppressors were isolated which recovered the ability to utilize G-1-P as carbon source. The mutants constitutively expressed hexose phosphate permease activity (encoded by uhpT). The mutation involved mapped in the uhp region and, unlike those of wild-type strains, bacteria of the suppressed strains required phosphoglucomutase (pgm), to grow on G-1-P. Surprisingly, in a minimal medium deprived of inorganic phosphate, uhpT+ bacteria lacking the two enzymes, alkaline-phosphatase (phoA) and glucose-1-phosphatase (agp), could utilize G-1-P as the sole source of phosphate, and also as both the sole phosphate and carbon source provided the integrity of pgm and of uhpT was conserved. Although glucose-6-phosphate, the inducer of UhpT permease, was not present in the medium, the activity of uhpT was greatly stimulated by inorganic phosphate depletion. This phosphate-starvation-induced bypass of G-1-Pase by UhpT + Pgm systems shows that agp is essential for G-1-P assimilation as a carbon source only in a high-phosphate medium, a result in agreement with the lack of agp regulation by inorganic phosphate.
Pradel
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Département de Biologie, CEN Saclay, Gif-sur-Yvette, France.
Boquet
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D000469:Alkaline Phosphatase / Q000502:physiology; D002244:Carbon / Q000378:metabolism; D003470:Culture Media; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial / Q000502:physiology; D005838:Genotype; D005958:Glucosephosphates / Q000378:metabolism*; D006600:Hexosephosphates / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000502:physiology; D009154:Mutation; D010710:Phosphates / Q000378:metabolism; D010733:Phosphoglucomutase / Q000502:physiology; D010744:Phosphoric Monoester Hydrolases / Q000502:physiology
D003470:Culture Media; D029968:Escherichia coli Proteins; D005958:Glucosephosphates; D006600:Hexosephosphates; D026901:Membrane Transport Proteins; D010710:Phosphates; D002244:Carbon; C031590:glucose-1-phosphate; D000469:Alkaline Phosphatase; C062887:agp protein, E coli; D010744:Phosphoric Monoester Hydrolases; D010733:Phosphoglucomutase