RRC ID 15838
Author Kiyohara M, Tanigawa K, Chaiwangsri T, Katayama T, Ashida H, Yamamoto K.
Title An exo-alpha-sialidase from bifidobacteria involved in the degradation of sialyloligosaccharides in human milk and intestinal glycoconjugates.
Journal Glycobiology
Abstract Bifidobacteria are health-promoting enteric commensals that are assumed to proliferate predominantly in the intestines of breast-fed infants by assimilating human milk oligosaccharides (HMOs) that are frequently fucosylated and/or sialylated. We previously identified two different α-l-fucosidases in Bifidobacterium bifidum and showed that the strain furnishes an extracellular degradation pathway for fucosylated HMOs. However, the catabolism of sialylated HMOs by bifidobacteria has remained unresolved. Here we describe the identification and characterization of an exo-α-sialidase in bifidobacteria. By expression cloning, we isolated a novel exo-α-sialidase gene (siabb2) from B. bifidum JCM1254, which encodes a protein (SiaBb2) consisting of 835-amino-acid residues with a predicted molecular mass of 87 kDa. SiaBb2 possesses an N-terminal signal sequence, a sialidase catalytic domain classified into the glycoside hydrolase family 33 (GH33) and a C-terminal transmembrane region, indicating that the mature SiaBb2 is an extracellular membrane-anchored enzyme. The recombinant enzyme expressed in Escherichia coli showed the highest activity in an acidic pH range from 4.0 to 5.0, and at 50 °C. Notably, 80% activity remained after 30 min incubation at 80 °C, indicating that the enzyme is highly thermostable. SiaBb2 liberated sialic acids from sialyloligosaccharides, gangliosides, glycoproteins and colominic acid; however, the linkage preference of the enzyme was remarkably biased toward the α2,3-linkage rather than α2,6- and α2,8-linkages. Expression of siabb2 in B. longum 105-A, which has no endogenous exo-α-sialidase, enabled this strain to degrade sialyloligosaccharides present in human milk. Our results suggest that SiaBb2 plays a crucial role in bifidobacterial catabolism of sialylated HMOs.
Volume 21(4)
Pages 437-47
Published 2011-4
DOI 10.1093/glycob/cwq175
PII cwq175
PMID 21036948
MeSH Amino Acid Sequence Bifidobacterium / enzymology* Cloning, Molecular Enzyme Assays Enzyme Stability Glycosylation Humans Milk, Human / metabolism* Molecular Sequence Data N-Acetylneuraminic Acid / metabolism Neuraminidase / chemistry* Neuraminidase / genetics Neuraminidase / metabolism Oligosaccharides / metabolism* Phylogeny Recombinant Proteins / chemistry* Recombinant Proteins / genetics Recombinant Proteins / metabolism Sequence Alignment Substrate Specificity Temperature
IF 3.664
Times Cited 36
General Microbes JCM 1254 JCM 7004 JCM 1222