title: Transport of N-acetyl-D-galactosamine in Escherichia coli K92: effect on acetyl-amino sugar metabolism and polysialic acid production.
abstract: The N-acetyl-D-galactosamine (GalNAc) transport system of Escherichia coli K92 was studied when the bacterium was grown in a chemically defined medium containing GalNAc as a carbon source. Kinetic measurements were carried out in vivo at 37 degrees C in 25 mM phosphate buffer, pH 7.0. Under these conditions, the uptake rate was linear for at least 3 min and the calculated Km for GalNAc was 3 microM. The transport system was strongly inhibited by sodium arsenate (70%), potassium cyanide (62%) and 2,4-dinitrophenol (75%). Analysis of bacterial GalNAc phosphotransferase activity revealed in vitro GalNAc phosphorylation activity only when phosphoenolpyruvate was present. These results strongly support the notion that GalNAc uptake depends on a specific phosphotransferase system. Study of activity regulation showed that N-acetylglucosamine and mannosamine specifically inhibit the transport of GalNAc in this bacterium. Analysis of expression revealed that the GalNAc transport system is specifically induced by GalNAc but not by N-acetylglucosamine (GlcNAc) or N-acetylmannosamine (ManNAc), two intimately related sugars. Moreover, full induction of GalNAc transport required the presence of both cAMP and GalNAc. Comparative studies revealed that E. coli K92 has developed a regulation mechanism that specifically induces the appropriate permease based on the presence of each respective phospho-amino sugar (GlcNAc, ManNAc and GalNAc). In this regulation system, GlcNAc is the preferred amino sugar as the carbon source. Finally, when E. coli K92 was grown using GalNAc, capsular polysialic acid production was strongly affected. The presence of intracellular phosphoderivative acetylamino sugars, generated by the action of the phosphotransferase transport system, can be responsible for this effect.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Universidad de León, Campus de Vegazana, 24007 León, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Ezquerro-Sáenz
authors.forename: M A
authors.initials: MA
authors.lastname: Ferrero
authors.forename: B
authors.initials: B
authors.lastname: Revilla-Nuin
authors.forename: F F
authors.initials: FF
authors.lastname: López Velasco
authors.forename: H
authors.initials: H
authors.lastname: Martínez-Blanco
authors.forename: L B
authors.initials: LB
authors.lastname: Rodríguez-Aparicio
mesh_terms: D000116:Acetylgalactosamine / Q000378:metabolism*; D000117:Acetylglucosamine / Q000494:pharmacology; D000606:Amino Sugars / Q000378:metabolism*; D003470:Culture Media; D000242:Cyclic AMP / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism*; D006595:Hexosamines / Q000494:pharmacology; D007700:Kinetics; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism; D012794:Sialic Acids / Q000096:biosynthesis*
chemical_list: D000606:Amino Sugars; D003470:Culture Media; D006595:Hexosamines; D009004:Monosaccharide Transport Proteins; D012794:Sialic Acids; C021319:polysialic acid; D000242:Cyclic AMP; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D000116:Acetylgalactosamine; D000117:Acetylglucosamine; C002022:N-acetylmannosamine