Identification of the cellobiose 2-epimerase gene in the genome of Bacteroides fragilis NCTC 9343.
Cellobiose 2-epimerase (CE, EC 5.1.3.11) catalyzes the reversible epimerization of cellobiose to 4-O-beta-D-glucopyranosyl-D-mannose. In this study, we found a CE gene in the genome sequence of non-cellulolytic Bacteroides fragilis NCTC 9343. The recombinant enzyme, expressed in Escherichia coli cells, catalyzed a hydroxyl stereoisomerism at the C-2 positions of the reducing terminal glucose and at the mannose moiety of cello-oligosaccharides, lactose, beta-mannobiose (4-O-beta-D-mannopyranosyl-D-mannose), and globotriose [O-alpha-D-galactopyranosyl-(1-->4)-O-beta-D-galactopyranosyl-(1-->4)-D-glucose]. The CE from B. fragilis showed less than 40% identity to reported functional CEs. It exhibited 44-63% identities to N-acyl-D-glucosamine 2-epimerase-like hypothetical proteins of unknown function in bacterial genome sequences of the phyla Firmicutes, Bacteroidetes, Proteobacteria, Chloroflexi, and Verrucomicrobia. On the other hand, it showed less than 26% identity to functional N-acyl-D-glucosamine 2-epimerases. Based on the amino acid homology and phylogenetic positions of the functional epimerases, we emphasize that many genes for putative N-acyl-D-glucosamine 2-epimerases and related hypothetical proteins of unknown function reported to date in the bacterial genomes should be annotated as CE-like proteins or putative CEs.
Senoura
Takeshi
T
Creative Research Initiative Sousei (CRIS), Hokkaido University, Sapporo, Japan.
Taguchi
Hidenori
H
Ito
Shigeaki
S
Hamada
Shigeki
S
Matsui
Hirokazu
H
Fukiya
Satoru
S
Yokota
Atsushi
A
Watanabe
Jun
J
Wasaki
Jun
J
Ito
Susumu
S
D000595:Amino Acid Sequence; D001441:Bacteroides fragilis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics*; D055162:Biocatalysis; D002238:Carbohydrate Epimerases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D002475:Cellobiose / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D013379:Substrate Specificity; D013696:Temperature
D002475:Cellobiose; D002238:Carbohydrate Epimerases