title: Bifidobacterium bifidum lacto-N-biosidase, a critical enzyme for the degradation of human milk oligosaccharides with a type 1 structure.
abstract: Breast-fed infants often have intestinal microbiota dominated by bifidobacteria in contrast to formula-fed infants. We found that several bifidobacterial strains produce a lacto-N-biosidase that liberates lacto-N-biose I (Galbeta1,3GlcNAc; type 1 chain) from lacto-N-tetraose (Galbeta1,3GlcNAcbeta1,3Galbeta1,4Glc), which is a major component of human milk oligosaccharides, and subsequently isolated the gene from Bifidobacterium bifidum JCM1254. The gene, designated lnbB, was predicted to encode a protein of 1,112 amino acid residues containing a signal peptide and a membrane anchor at the N and C termini, respectively, and to possess the domain of glycoside hydrolase family 20, carbohydrate binding module 32, and bacterial immunoglobulin-like domain 2, in that order, from the N terminus. The recombinant enzyme showed substrate preference for the unmodified beta-linked lacto-N-biose I structure. Lacto-N-biosidase activity was found in several bifidobacterial strains, but not in the other enteric bacteria, such as clostridia, bacteroides, and lactobacilli, under the tested conditions. These results, together with our recent finding of a novel metabolic pathway specific for lacto-N-biose I in bifidobacterial cells, suggest that some of the bifidobacterial strains are highly adapted for utilizing human milk oligosaccharides with a type 1 chain.
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Wada
authors.forename: Takuro
authors.initials: T
authors.lastname: Ando
authors.forename: Masashi
authors.initials: M
authors.lastname: Kiyohara
authors.forename: Hisashi
authors.initials: H
authors.lastname: Ashida
authors.forename: Motomitsu
authors.initials: M
authors.lastname: Kitaoka
authors.forename: Masanori
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Kumagai
authors.forename: Takane
authors.initials: T
authors.lastname: Katayama
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001644:Bifidobacterium / Q000145:classification / Q000201:enzymology*; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D008895:Milk, Human / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D009844:Oligosaccharides; D011994:Recombinant Proteins; D006026:Glycoside Hydrolases; C076748:lacto-N-biosidase