Homology Modeling and Active Sites of PolyMG-specific Alginate Lyase from Stenotrophomonas maltophilia KJ-2

摘要: Alginates are linear acidic polysaccharides composed with (1-4)-linked α-L-guluronic acid and β-Dmannuronic acid. Alginate can be degraded by diverse alginate lyases, which cleave the using a β-elimination reaction produce unsaturated uronate oligomers. A gene for polyMG-specific lyase possessing novel structure was previously identified cloned from Stenotrophomonas maltophilia KJ-2. Homology modeling of KJ-2 showed it belongs to PL6 family, whereas three Azotobacter vinelandii polyMG lyases belong PL7 family polysaccharide lyases. From H-NMR spectra data, preferably M-β(1-4)-G glycosidic bond than G-α(1-4)-M bond. Seventeen mutants were made site-directed mutagenesis, activity analyzed. Lys220Ala, Arg241Ala, Arg241Lys, Arg265Ala lost completely. Arg155Ala, Gly303Glu, Tyr304Phe also 60.7-80.1%. These results show that Arg155, Lys220, Arg241, Arg265, Gly303, Tyr304 important residues catalytic substrate binding.