Biochemical and Structural Characterization of Alginate Lyases: An Update

Abstract

Background: Alginates, a complex copolymer of α-L-guluronate (G) and its C5 epimer β-Dmannuronate (M), can be disassembled by alginate lyases to monosaccharides or alginate oligosaccharides, and the latter exhibits many fascinating bioactivities. A lot of new alginate lyases have been identified in many resources, especially in marine organisms. Elucidating the natural paradigms of alginate conversion will enable us to utilize algal biomass efficiently and enhance our understanding of how microorganisms evolved with plants. Crystal structures of different polysaccharide lyase (PL) families have been solved by X-ray diffraction, which will improve our understanding in molecule-level catalytic mechanisms. Methods: The researches related to alginate lyases after 2000 are reviewed, and data is sorted and analyzed. Protein sequences alignment and phylogenetic tree are employed to discuss different groups of alginate lyases. Furthermore, viewpoints about the studies of alginate lyases are proposed. Results: In this review, the latest resources of alginate lyases are summarized, progress of alginate lyases on structuralfunctional relationships are presented. The biochemical characterization, biological role, and the promising applications of alginate lyases also are discussed. Conclusion: New alginate lyases have sprung up throughout the marine and terrestrial organisms. Structure-function analyses of alginate lyases will shed light on the understanding of catalytic mechanism of alginate lyases. However, the mechanisms of bioactivities of alginates are still unclear. Extensive investigation of alginate lyases is crucial for the development of alginate applications. Besides, a standard and meaningful naming system for alginate lyases may be needed. Keywords: Alginate lyases, active site, catalytic mechanism, conservative sequence, crystal structure, polysaccharide lyase.