6hh9

Crystal structure of a two-domain esterase (CEX) active on acetylated mannans co-crystallized with mannopentaose

spinqualitylabelsall models 6hh9, resolution 2.40Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6hh9 is a 4 chain structure with sequence from Roseburia intestinalis l1-82. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: BMA Related: 6hfz Gene: ROSINTL182_05471 (Roseburia intestinalis L1-82) Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed beta-mannans and xylans are important components of the plant cell wall and they are acetylated to be protected from degradation by glycoside hydrolases. beta-mannans are widely present in human and animal diets as fiber from leguminous plants and as thickeners and stabilizers in processed foods. There are many fully characterized acetylxylan esterases (AcXEs); however, the enzymes deacetylating mannans are less understood. Here we present two carbohydrate esterases, RiCE2 and RiCE17, from the Firmicute Roseburia intestinalis, which together deacetylate complex galactoglucomannan (GGM). The three-dimensional (3D) structure of RiCE17 with a mannopentaose in the active site shows that the CBM35 domain of RiCE17 forms a confined complex, where the axially oriented C2-hydroxyl of a mannose residue points toward the Ser41 of the catalytic triad. Cavities on the RiCE17 surface may accept galactosylations at the C6 positions of mannose adjacent to the mannose residue being deacetylated (subsite -1 and +1). In-depth characterization of the two enzymes using time-resolved NMR, high-performance liquid chromatography (HPLC), and mass spectrometry demonstrates that they work in a complementary manner. RiCE17 exclusively removes the axially oriented 2-O-acetylations on any mannose residue in an oligosaccharide, including double acetylated mannoses, while the RiCE2 is active on 3-O-, 4-O-, and 6-O-acetylations. Activity of RiCE2 is dependent on RiCE17 removing 2-O-acetylations from double acetylated mannose. Furthermore, transacetylation of oligosaccharides with the 2-O-specific RiCE17 provided insight into how temperature and pH affects acetyl migration on manno-oligosaccharides. A pair of esterases from a commensal gut bacterium remove acetylations from all positions on complex beta-mannans.,Michalak L, La Rosa SL, Leivers S, Lindstad LJ, Rohr AK, Lillelund Aachmann F, Westereng B Proc Natl Acad Sci U S A. 2020 Mar 13. pii: 1915376117. doi:, 10.1073/pnas.1915376117. PMID:32170022 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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