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KMID : 0613820150250020121
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Journal of Life Science
2015 Volume.25 No. 2 p.121 ~ p.129
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Homology Modeling and Characterization of Oligoalginate Lyase from the Alginolytic Marine Bacterium Sphingomonas sp. Strain MJ-3
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Kim Hee-Sook
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Abstract
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Alginates are found in marine brown seaweeds and in extracellular biofilms secreted by some bacteria. Previously, we reported an oligoalginate lyase from Sphingomonas sp. MJ-3 (MJ3-Oal) that had an exolytic activity and protein sequence homology with endolytic polymannuronate (polyM) lyase in the N-terminal region. In this study, the MJ3-Oal was tested for both exolytic and endolytic activity by homology modeling using the crystal structure of Alg17c from Saccharophagus degradans 2-40T. The tyrosine residue at the 426th position, which possibly formed a hydrogen bond with the substrate, was mutated to phenylalanine. The FPLC profiles showed that MJ3-Oal degraded alginate quickly to monomers as a final product through the oligmers, whereas the Tyr426Phe mutant showed only exolytic alginate lyase activity. 1H-NMR spectra also showed that MJ3-Oal degraded the endoglycosidic bond of polyM and polyMG (polymannuronate-guluronate) blocks. These results indicate that oligoalginate lyase from Sphingomonas sp. MJ-3 probably catalyzes the degradation of both exo- and endo-glycosidic bonds of alginate.
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KEYWORD
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Endolytic activity, exolytic activity, homology modeling, oligoalginate lyase
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