NCBI PubMed ID:10347037 Journal NLM ID:7605801 Publisher: American Society for Microbiology Correspondence: hasimotofood2.food.kyoto-u.ac.jp Institutions: Research Institute for Food Science, Kyoto University, Uji 611-0011, Japan
An enzymatic route for the depolymerization of a heteropolysaccharide (xanthan) in Bacillus sp. strain GL1, which was closely related to Brevibacillus thermoruber, was determined by analyzing the structures of xanthan depolymerization products. The bacterium produces extracellular xanthan lyase catalyzing the cleavage of the glycosidic bond between pyruvylated mannosyl and glucuronyl residues in xanthan side chains (W. Hashimoto et al., Appl. Environ. Microbiol. 64:3765-3768, 1998). The modified xanthan after the lyase reaction was then depolymerized by extracellular β-D-glucanase to a tetrasaccharide, without the terminal mannosyl residue of the side chain in a pentasaccharide, a repeating unit of xanthan. The tetrasaccharide was taken into cells and converted to a trisaccharide (unsaturated glucuronyl-acetylated mannosyl-glucose) by β-D-glucosidase. The trisaccharide was then converted to the unsaturated glucuronic acid and a disaccharide (mannosyl-glucose) by unsaturated glucuronyl hydrolase. Finally, the disaccharide was hydrolyzed to mannose and glucose by α-D-mannosidase. This is the first complete report on xanthan depolymerization by bacteria. Novel β-D-glucanase, one of the five enzymes involved in the depolymerization route, was purified from the culture fluid. This enzyme was a homodimer with a subunit molecular mass of 173 kDa and was most active at pH 6.0 and 45 degrees C. The enzyme specifically acted on xanthan after treatment with xanthan lyase and released the tetrasaccharide.
Methods: SDS-PAGE, ESI-MS, enzymatic degradation, RNA analysis Enzymes that release or process the structure: xanthan lyase, b-D-glucanase, b-D-glucosidase, unsaturated glucuronyl hydrolase, a-D-mannosidase Comments, role: product of xanthan depolymerization by xanthan lygase, b-D-glucanase, b-D-glucosidase, and unsaturated glucuronyl hydrolase
Related record ID(s): 7748, 7843, 7844, 7845, 7847, 7848, 20400 NCBI Taxonomy refs (TaxIDs):84635 Reference(s) to other database(s): GTC:G85855EZ, GlycomeDB:27202 Show glycosyltransferases
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