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Glycoside Hydrolase Family 136

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Glycoside Hydrolase Family GH136
Clan GH-N
Mechanism retaining
Active site residues Asp
CAZy DB link

Substrate specificities

This family of glycoside hydrolases contains lacto-N-biosidase, as demonstrated for LnbX from Bifidobacterium longum JCM 1217 [1]. LnbX liberates Galβ1-3GlcNAc(lacto-N-biose I, LNB) and lactose from lacto-N-tetraose, the main component of human milk oligosaccharides. It hydrolyzed the linkage GlcNAcβ1-3Gal in lacto-N-hexaose, lacto-N-fucopentaose I, and sialyllacto-N-tetraose a of human milk oligosaccharides as substrate of LnbX in the GH136. In addition, LnbX liberates Galβ1-3GalNAc (GNB) from the sugar chains of globo- and ganglio-series glycosphingolipids [2].

GH136 lacto-N-biosidase required neighboring chaperon gene for folding. Rarely, chaperone-like gene fused to lacto-N-biosidase gene in case of ErLnb136I and ErLnb136IIfrom Eubacterium ramulus [3].

Kinetics and Mechanism

LnbX hydrolyzes the glycosidic linkage via a retaining mechanism involving a Grotthuss proton relay.

Catalytic Residues

The nucleophile is Asp418. The catalytic acid/base is Asp411 via water molecule.

Three-dimensional structures

Figure 1: Overall structure of LnbXc with LNB (cyan) and two Ca2+ ions (orange).
Figure 2: Overall structure of ErLnb136 with LNB (yellow), consisting of an N-terminal domain designated as ErLnb136I (cyan-blue) and a C-terminal β-helix domain (green) -ErLnb136II.

The X-ray crystal structure of the catalytic domain, LnbXc(31-625) revealed a right-handed β helix fold that is usually shared by polysaccharide active enzymes. Three forms, ligand free at 2.36 Å resolution (PDB ID 5GQC), LNB complex at 1.82 Å (PDB ID 5GQF), and GNB complex at 2.70 Å (PDB ID 5GQG) were determined [4]. The X-ray crystal structure of ErGH136 in complex with LNB (PDB ID 6KQT) revealed the N-terminal domain (ErLnb136I, from AA 7-224) consists of 8 α-helices (α1-α8) and Y145 of the α6-α7 loop positioned near the active site [3].

Family Firsts

First stereochemistry determination
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First catalytic nucleophile identification
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First general acid/base residue identification
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First 3-D structure
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  1. Sakurama H, Kiyohara M, Wada J, Honda Y, Yamaguchi M, Fukiya S, Yokota A, Ashida H, Kumagai H, Kitaoka M, Yamamoto K, and Katayama T. (2013) Lacto-N-biosidase encoded by a novel gene of Bifidobacterium longum subspecies longum shows unique substrate specificity and requires a designated chaperone for its active expression. J Biol Chem. 288, 25194-206. DOI:10.1074/jbc.M113.484733 | PubMed ID:23843461 | HubMed [Sakurama2013]
  2. Gotoh A, Katoh T, Sugiyama Y, Kurihara S, Honda Y, Sakurama H, Kambe T, Ashida H, Kitaoka M, Yamamoto K, and Katayama T. (2015) Novel substrate specificities of two lacto-N-biosidases towards β-linked galacto-N-biose-containing oligosaccharides of globo H, Gb5, and GA1. Carbohydr Res. 408, 18-24. DOI:10.1016/j.carres.2015.03.005 | PubMed ID:25839135 | HubMed [Gotoh2015]
  3. Pichler MJ, Yamada C, Shuoker B, Alvarez-Silva C, Gotoh A, Leth ML, Schoof E, Katoh T, Sakanaka M, Katayama T, Jin C, Karlsson NG, Arumugam M, Fushinobu S, and Abou Hachem M. (2020) Butyrate producing colonic Clostridiales metabolise human milk oligosaccharides and cross feed on mucin via conserved pathways. Nat Commun. 11, 3285. DOI:10.1038/s41467-020-17075-x | PubMed ID:32620774 | HubMed [Michael2020]
  4. Yamada C, Gotoh A, Sakanaka M, Hattie M, Stubbs KA, Katayama-Ikegami A, Hirose J, Kurihara S, Arakawa T, Kitaoka M, Okuda S, Katayama T, and Fushinobu S. (2017) Molecular Insight into Evolution of Symbiosis between Breast-Fed Infants and a Member of the Human Gut Microbiome Bifidobacterium longum. Cell Chem Biol. 24, 515-524.e5. DOI:10.1016/j.chembiol.2017.03.012 | PubMed ID:28392148 | HubMed [chihaya2017]
All Medline abstracts: PubMed | HubMed