Metabolism of sugars by genetically diverse species of oral Leptotrichia.
Leptotrichia buccalis ATCC 14201 is a gram-negative, anaerobic rod-shaped bacterium resident in oral biofilm at the tooth surface. The sequenced genome of this organism reveals three contiguous genes at loci: Lebu_1525, Lebu_1526 and Lebu_1527. The translation products of these genes exhibit significant homology with phospho-α-glucosidase (Pagl), a regulatory protein (GntR) and a phosphoenol pyruvate-dependent sugar transport protein (EIICB), respectively. In non-oral bacterial species, these genes comprise the sim operon that facilitates sucrose isomer metabolism. Growth studies showed that L. buccalis fermented a wide variety of carbohydrates, including four of the five isomers of sucrose. Growth on the isomeric disaccharides elicited expression of a 50-kDa polypeptide comparable in size to that encoded by Lebu_1525. The latter gene was cloned, and the expressed protein was purified to homogeneity from Escherichia coli TOP10 cells. In the presence of two cofactors, NAD(+) and Mn(2+) ions, the enzyme readily hydrolyzed p-nitrophenyl-α-glucopyranoside 6-phosphate (pNPαG6P), a chromogenic analogue of the phosphorylated isomers of sucrose. By comparative sequence alignment, immunoreactivity and signature motifs, the enzyme can be assigned to the phospho-α-glucosidase (Pagl) clade of Family 4 of the glycosyl hydrolase super family. We suggest that the products of Lebu_1527 and Lebu_1525, catalyze the phosphorylative translocation and hydrolysis of sucrose isomers in L. buccalis, respectively. Four genetically diverse, but 16S rDNA-related, species of Leptotrichia have recently been described: L. goodfellowii, L. hofstadii, L. shahii and L. wadei. The phenotypic traits of these new species, with respect to carbohydrate utilization, have also been determined.
Microbial Biochemistry and Genetics Unit, Oral Infection and Immunity Branch, NIDCR, National Institutes of Health, Bethesda, MD 20892, USA. jthompson@dir.nidcr.nih.gov
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D001426:Bacterial Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D003773:Dental Plaque / Q000382:microbiology; D004186:Disaccharidases / Q000378:metabolism*; D005798:Genes, Bacterial; D006026:Glycoside Hydrolases / Q000235:genetics; D007527:Isoenzymes; D045183:Leptotrichia / Q000235:genetics* / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D010766:Phosphorylation / Q000235:genetics; D013045:Species Specificity; D013395:Sucrose / Q000378:metabolism*; D000520:alpha-Glucosidases / Q000235:genetics
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D009004:Monosaccharide Transport Proteins; D013395:Sucrose; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D004186:Disaccharidases; D006026:Glycoside Hydrolases; D000520:alpha-Glucosidases