title: Fructoselysine 3-epimerase, an enzyme involved in the metabolism of the unusual Amadori compound psicoselysine in Escherichia coli.
abstract: The frl (fructoselysine) operon encodes fructoselysine 6-kinase and fructoselysine 6-phosphate deglycase, allowing the conversion of fructoselysine into glucose 6-phosphate and lysine. We now show that a third enzyme encoded by this operon catalyses the metal-dependent reversible interconversion of fructoselysine with its C-3 epimer, psicoselysine. The enzyme can be easily assayed through the formation of tritiated water from [3-3H]fructoselysine. Psicoselysine supports the growth of Escherichia coli, causing the induction of the three enzymes of the frl operon. No growth on fructoselysine or psicoselysine was observed with Tn5 mutants in which the putative transporter (FrlA) or fructoselysine 6-phosphate deglycase (FrlB) had been inactivated, indicating the importance of the frl operon for the metabolism of both substrates. The ability of E. coli to grow on psicoselysine suggests the occurrence of this unusual Amadori compound in Nature.
authors.affiliation: Laboratory of Physiological Chemistry, Christian de Duve Institute of Cellular Pathology and Université Catholique de Louvain, Avenue Hippocrate 75, B-1200 Brussels, Belgium.
authors.forename: Elsa
authors.initials: E
authors.lastname: Wiame
authors.forename: Emile
authors.initials: E
authors.lastname: Van Schaftingen
mesh_terms: D000595:Amino Acid Sequence; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D002384:Catalysis; D002455:Cell Division; D004926:Escherichia coli / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D006601:Hexoses / Q000378:metabolism*; D007700:Kinetics; D008239:Lysine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D019998:Racemases and Epimerases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D016415:Sequence Alignment
chemical_list: D006601:Hexoses; C487221:psicoselysine; C033186:fructosyl-lysine; D019998:Racemases and Epimerases; D002238:Carbohydrate Epimerases; C487220:fructoselysine 3-epimerase; D008239:Lysine