Characterization of genes involved in fructose utilization by Lactobacillus fermentum.
The genes encoding phosphoglucose isomerase (fruI) and fructokinase (fruK) of Lactobacillus fermentum NRRL-B-1932 were sequenced. They constituted an operon, which is involved in fructose metabolism of this strain by channeling intracellular fructose into the phosphoketolase pathway. A third open reading frame, unkR, upstream of the operon was identified as homologous to genes of LacI/GalR family repressors. The UnkR repressor's role in transcriptional control of the fruIK operon could, however, not be established by electrophoretic mobility shift assay (EMSA) analysis. Sequence analysis revealed two putative catabolite responsive elements (cre) in the promoter region of fruIK suggesting that the fruIK operon is under negative regulatory control by carbon catabolite repression. Expression and enzyme activity data were compatible with the assumption that the fruIK operon is repressed by glucose. No sugar specific phosphoenolpyruvate sugar transferase system activity for the transport of fructose, glucose, sucrose or mannose could be detected in L. fermentum NRRL-B-1932 cells, which suggest that fructose is taken up by a permease system.
Helanto
Miia
M
Laboratory of Bioprocess Engineering, Department of Chemical Technology, Helsinki University of Technology, P.O. Box 9400, 02015 Espoo, Finland. miia.helanto@hut.fi
Aarnikunnas
Johannes
J
Palva
Airi
A
Leisola
Matti
M
Nyyssölä
Antti
A
D001483:Base Sequence; D003001:Cloning, Molecular; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D005631:Fructokinases / Q000235:genetics* / Q000378:metabolism; D005632:Fructose / Q000378:metabolism*; D005956:Glucose-6-Phosphate Isomerase / Q000235:genetics* / Q000378:metabolism; D052197:Limosilactobacillus fermentum / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009876:Operon; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
D012333:RNA, Messenger; D005632:Fructose; D005631:Fructokinases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C046173:fructokinase; D005956:Glucose-6-Phosphate Isomerase