title: L-guluronan-specific alginate lyase from a marine bacterium associated with Sargassum.
abstract: The major extracellular alginate lyase activities secreted by a Gram-negative, facultative bacterium associated with actively growing Sargassum fluitans have been resolved an examined for substrate specificity. A fraction excluded from Sephadex G-75 was equally active toward (1----4)-beta-D-mannuronan, (1----4)-alpha-L-guluronan, and alginate with the formation of di- and tri-saccharides as apparent limit products and oligo-saccharides indicative of an endolytic mechanism. A second fraction which was included during G-75 filtration was inactive toward D-mannuronan and 4 times more active toward L-guluronan than native alginate. Proton magnetic resonance spectrometry identified the primary product of this enzyme as O-(4-deoxy-alpha-L-erythro-hex-4-enopyranosyluronic acid)-(1----4)-O-(alpha-L-gulopyranosyluronic acid)-(1----4)-O-alpha-L-gulopyranuronic acid. The L-guluronan-specific enzyme requires 0.5 M NaCl for maximal activity and has been purified as a monomeric protein having an apparent molecular mass of 38 kD and an approximate pI of 4.5. The predominant formation of trisaccharide over the course of a reaction showed a primarily exolytic mechanism, indicating an enzyme activity unique from any previously reported.
authors.affiliation: Department of Microbiology and Cell Science, University of Florida, Gainesville 32611-0116.
authors.forename: B J
authors.initials: BJ
authors.lastname: Brown
authors.forename: J F
authors.initials: JF
authors.lastname: Preston
mesh_terms: D002240:Carbohydrate Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D006090:Gram-Negative Bacteria / Q000201:enzymology* / Q000254:growth & development; D007525:Isoelectric Focusing; D008969:Molecular Sequence Data; D000459:Phaeophyceae; D011133:Polysaccharide-Lyases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D014312:Trisaccharides / Q000378:metabolism*
chemical_list: D014312:Trisaccharides; D011133:Polysaccharide-Lyases; C016158:poly(beta-D-mannuronate) lyase