Endo-β-N-acetylglucosaminidases from Infant Gut-associated Bifidobacteria Release Complex N-glycans from Human Milk Glycoproteins

Abstract

Breastfeeding is one of the main factors guiding the composition of the infant gut microbiota in the first months of life. This process is shaped in part by the high amounts of human milk oligosaccharides that serve as a carbon source for saccharolytic bacteria such as Bifidobacterium species. Infant-borne bifidobacteria have developed various molecular strategies for utilizing these oligosaccharides as a carbon source. We hypothesized that these species also interact with N-glycans found in host glycoproteins that are structurally similar to free oligosaccharides in human milk. Endo-␤-Nacetylglucosaminidases were identified in certain isolates of Bifidobacterium longum subsp. longum, B. longum subsp. infantis, and Bifidobacterium breve, and their presence correlated with the ability of these strains to deglycosylate glycoproteins. An endoglycosidase from B. infantis ATCC 15697, EndoBI-1, was active toward all major types of N-linked glycans found in glycosylated proteins. Its activity was not affected by core fucosylation or extensive fucosylation, antenna number, or sialylation, releasing several N-glycans from human lactoferrin and immunoglobulins A and G. Extensive N-deglycosylation of whole breast milk was also observed after coincubation with this enzyme. Mutation of the active site of EndoBI-1 did not abolish binding to N-glycosylated proteins, and this mutant specifically recognized Man 3 GlcNAc 2 (␣1-6Fuc), the core structure of human N-glycans. EndoBI-1 is constitutively expressed in B. infantis, and incubation of the bacterium with human or bovine lactoferrin led to the induction of genes associated to import and consumption of human milk oligosaccharides, suggesting linked regulatory mechanisms among these glycans. This work reveals an unprecedented interaction of bifidobacteria with host

Metabolism of Sialic Acid by Bifidobacterium breve UCC2003

“…breve strains represent a dominant commensal group in the breast-fed infant gut microbiota, but it is only recently that the factors that contribute to this dominance have become a subject of scientific scrutiny. It has already been shown that B. breve strains can liberate N-glycans from host glycoproteins and glycoproteins from breast milk (65), and a more recent study has demonstrated that B. breve strains can grow on the HMOs lacto-N-tetraose, lacto-N-neotetraose, and sialylated lacto-N-tetraose (35). In this report, we describe the functional characterization of a locus dedicated to the uptake and utilization of sialic acid.…”

Variation in Consumption of Human Milk Oligosaccharides by Infant Gut-Associated Strains of Bifidobacterium breve

“…Unfortunately, the factors that contribute to this persistence in infants are not well understood. We have previously determined that some B. breve strains are equipped with enzymes that release N-glycans from host glycoproteins, and some strains can use N-glycosylated proteins as the sole carbon source (31). This suggested that glycoproteins could play a prebiotic role for B. breve.…”

Isolation of a Bifidogenic Peptide from the Pepsin Hydrolysate of Bovine Lactoferrin

“…In B. longum subsp. infantis, it is reported that genes that are necessary for the utilization of human milk oligosaccharide were upregulated by hLF or bLF (31). LF might stimulate the incorporation of nutrients from the environment.…”