Identification of a pathway for the utilization of the Amadori product fructoselysine in Escherichia coli

Escherichia coli was found to grow on fructoselysine as an energetic substrate at a rate of about one-third of that observed with glucose. Extracts of cells grown on fructoselysine catalyzed in the presence of ATP the phosphorylation of fructoselysine and a delayed formation of glucose 6-phosphate from this substrate. Data base searches allowed us to identify an operon containing a putative kinase (YhfQ) belonging to the PfkB/ ribokinase family, a putative deglycase (YhfN), homologous to the isomerase domain of glucosamine-6-phosphate synthase, and a putative cationic amino acid transporter (YhfM). The proteins encoded by YhfQ and YhfN were overexpressed in E. coli, purified, and shown to catalyze the ATP-dependent phosphorylation of fructoselysine to a product identified as fructoselysine 6-phosphate by 31P NMR (YhfQ), and the reversible conversion of fructoselysine 6-phosphate and water to lysine and glucose 6-phosphate (YhfN). The K(m) of the kinase for fructoselysine amounted to 18 microm, and the K(m) of the deglycase for fructoselysine 6-phosphate, to 0.4 mm. A value of 0.15 m was found for the equilibrium constant of the deglycase reaction. The kinase and the deglycase were both induced when E. coli was grown on fructoselysine and then reached activities sufficient to account for the rate of fructoselysine utilization.