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From Proteopedia
Structure of the N-acetyl-D-glucosamine oxidase from Ralstonia Solanacearum
Structural highlights
FunctionHEXNO_RALSU Catalyzes the oxidation of a range of monosaccharides in vitro, displaying the highest activity with N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc), with a reduction of O2 to H2O2. Acts upon the C1 carbon of the GlcNAc or GalNAc molecule, producing the corresponding lactone, which can spontaneously hydrolyze. Its biological function is unclear, but its main function might be connected to extracellular production of hydrogen peroxide to compete with other organisms through oxidative stress, or support the action of peroxidases and peroxygenases.[1] Publication Abstract from PubMedFlavin-dependent carbohydrate oxidases are valuable tools in biotechnological applications due to their high selectivity in the oxidation of carbohydrates. In this study, we report the biochemical and structural characterization of a recently discovered carbohydrate oxidase from the bacterium Ralstonia solanacearum, which is a member of the vanillyl alcohol oxidase flavoprotein family. Due to its exceptionally high activity toward N-acetyl-d-galactosamine and N-acetyl-d-glucosamine, the enzyme was named N-acetyl-glucosamine oxidase (NagOx). In contrast to most known (fungal) carbohydrate oxidases, NagOx could be overexpressed in a bacterial host, which facilitated detailed biochemical and enzyme engineering studies. Steady state kinetic analyses revealed that non-acetylated hexoses were also accepted as substrates albeit with lower efficiency. Upon determination of the crystal structure, structural insights into NagOx were obtained. A large cavity containing a bicovalently bound FAD, tethered via histidyl and cysteinyl linkages, was observed. Substrate docking highlighted how a single residue (Leu251) plays a key role in the accommodation of N-acetylated sugars in the active site. Upon replacement of Leu251 (L251R mutant), an enzyme variant was generated with a drastically modified substrate acceptance profile, tuned toward non-N-acetylated monosaccharides and disaccharides. Furthermore, the activity toward bulkier substrates such as the trisaccharide maltotriose was introduced by this mutation. Due to its advantage of being overexpressed in a bacterial host, NagOx can be considered a promising alternative engineerable biocatalyst for selective oxidation of monosaccharides and oligosaccharides. Structural Elucidation and Engineering of a Bacterial Carbohydrate Oxidase.,Boverio A, Widodo WS, Santema LL, Rozeboom HJ, Xiang R, Guallar V, Mattevi A, Fraaije MW Biochemistry. 2023 Jan 17;62(2):429-436. doi: 10.1021/acs.biochem.2c00307. Epub , 2022 Jul 26. PMID:35881507[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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