AUTHOR=Yang Min , Yu Yuan , Yang Suxiao , Shi Xiaohui , Mou Haijin , Li Li 

TITLE=Expression and Characterization of a New PolyG-Specific Alginate Lyase From Marine Bacterium Microbulbifer sp. Q7

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.02894

DOI=10.3389/fmicb.2018.02894

ISSN=1664-302X

ABSTRACT=<p>Alginate lyases play an important role in preparation of alginate oligosaccharides. Although a large number of alginate lyases have been characterized, reports on directional preparation of alginate oligosaccharides by alginate lyases are still rather less. Here, a gene <italic>alyM</italic> encoding a new alginate lyase AlyM was cloned from <italic>Microbulbifer</italic> sp. Q7 and expressed in <italic>Escherichia coli</italic>. AlyM exhibited the maximumactivity at pH 7.0 and 55°C and showed special preference to poly-guluronic acid (polyG). Glycine promoted the extracellular secretion of AlyM by 3.6 times. PBS and glycerol significantly improved the thermal stability of AlyM, the enzyme activity remained 75 and 78% after heat-treatment at 45°C for 2 h, respectively. ESI-MS analysis suggested that AlyM mainly produced oligosaccharides with degrees of polymerization (DP) of 2–5. The results of <sup>1</sup>H-NMR showed that guluronic acid (G) occupied the reducing end of the end products, indicating that AlyM preferred to degrade the glycosidic bond at the G-X linkage. HPLC analysis showed that the hydrolysis products with a lower degree of polymerization contained more G. Therefore, AlyM shows good potential to produce alginate oligosaccharides with specific M/G ratio and molecular weights.</p>