title: The Escherichia coli yjfP Gene Encodes a Carboxylesterase Involved in Sugar Utilization during Diauxie.
abstract: BACKGROUND
  Acetylation and efflux of carbohydrates during cellular metabolism is a well-described phenomenon associated with a detoxification process to prevent metabolic congestion. It is still unclear why cells discard important metabolizable energy sources in the form of acetylated compounds.
  
  
  METHODS
  We describe the purification and characterization of an approximately 28-kDa intracellular carboxylesterase (YjfP) and the analysis of gene and protein expression by qRT-PCR and Western blot.
  
  
  RESULTS
  qRT-PCR and Western blot, respectively, showed that yjfP is upregulated during the diauxic lag in cells growing with a mixture of glucose and lactose. The β-galactosidase activity in the ΔyjfP strain was both delayed and half the magnitude of that of the wild-type strain. YjfP-hyperproducing strains displayed a long lag phase when cultured with glucose and then challenged to grow with lactose or galactose as the sole carbon source.
  
  
  CONCLUSIONS
  Our results suggest that YjfP controls the intracellular concentration of acetyl sugars by redirecting them to the main metabolic circuits. Instead of detoxification, we propose that sugar acetylation is utilized by the cell for protection and to prevent the metabolism of a necessary minimal intracellular sugar pool. Those sugars can eventually be exported as a side effect of these mechanisms.
authors.affiliation: Genetics Institute, Department of Microbiology and Cell Science, Institute of Food and Agriculture Science, University of Florida, Gainesville, Fla., USA.
authors.forename: Nat
authors.initials: N
authors.lastname: Johns
authors.forename: Algevis
authors.initials: A
authors.lastname: Wrench
authors.forename: Flavia
authors.initials: F
authors.lastname: Loto
authors.forename: Ricardo
authors.initials: R
authors.lastname: Valladares
authors.forename: Graciela
authors.initials: G
authors.lastname: Lorca
authors.forename: Claudio F
authors.initials: CF
authors.lastname: Gonzalez
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western / Q000379:methods; D050260:Carbohydrate Metabolism; D043182:Carboxylesterase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004789:Enzyme Activation; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D018390:Gene Targeting; D005947:Glucose / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D016415:Sequence Alignment; D015854:Up-Regulation; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; C492127:YjgF protein, E coli; D043182:Carboxylesterase; D001616:beta-Galactosidase; D005947:Glucose; D007785:Lactose; D005690:Galactose