02484nas a2200433   4500000000100000008004100001260004400042653003400086653005700120653002200177653002200199100001600221700001500237700001400252700001600266700000900282700001600291700001200307700001500319700001300334700001100347700001500358700001400373700001100387700001400398700001400412700001300426700001500439700001300454700001000467700001600477700001300493245016000506856005900666300000900725490000700734520129500741022001402036       2023                            d  bSpringer Science and Business Media LLC10aGeneral Physics and Astronomy10aGeneral Biochemistry, Genetics and Molecular Biology10aGeneral Chemistry10amultidisciplinary1 aShimokawa M1 aIshiwata A1 aKashima T1 aNakashima C1 aLi J1 aFukushima R1 aSawai N1 aNakamori M1 aTanaka Y1 aKudo A1 aMorikami S1 aIwanaga N1 aAkai G1 aShimizu N1 aArakawa T1 aYamada C1 aKitahara K1 aTanaka K1 aIto Y1 aFushinobu S1 aFujita K00aIdentification and characterization of endo-α-, exo-α-, and exo-β-d-arabinofuranosidases degrading lipoarabinomannan and arabinogalactan of mycobacteria  uhttps://www.nature.com/articles/s41467-023-41431-2.pdf  a1-160 v143 a<p>The cell walls of pathogenic and acidophilic bacteria, such as Mycobacterium tuberculosis and Mycobacterium leprae, contain lipoarabinomannan and arabinogalactan. These components are composed of d-arabinose, the enantiomer of the typical l-arabinose found in plants. The unique glycan structures of mycobacteria contribute to their ability to evade mammalian immune responses. In this study, we identified four enzymes (two GH183 endo-d-arabinanases, GH172 exo-α-d-arabinofuranosidase, and GH116 exo-β-d-arabinofuranosidase) from Microbacterium arabinogalactanolyticum. These enzymes completely degraded the complex d-arabinan core structure of lipoarabinomannan and arabinogalactan in a concerted manner. Furthermore, through biochemical characterization using synthetic substrates and X-ray crystallography, we elucidated the mechanisms of substrate recognition and anomer-retaining hydrolysis for the α- and β-d-arabinofuranosidic bonds in both endo- and exo-mode reactions. The discovery of these d-arabinan-degrading enzymes, along with the understanding of their structural basis for substrate specificity, provides valuable resources for investigating the intricate glycan architecture of mycobacterial cell wall polysaccharides and their contribution to pathogenicity.</p>
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