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Mechanistic insights into substrate recognition and catalysis of a new ulvan lyase of polysaccharide lyase family 24

Xu, F, Dong, F, Sun, X-H, Cao, H-Y, Fu, H-H, Li, C-Y, Zhang, X-Y, McMinn, A ORCID: 0000-0002-2133-3854, Zhang, Y-Z, Wang, P and Chen, X-L 2021 , 'Mechanistic insights into substrate recognition and catalysis of a new ulvan lyase of polysaccharide lyase family 24' , Applied and Environmental Microbiology, vol. 87, no. 12 , pp. 1-13 , doi: 10.1128/AEM.00412-21.

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Ulvan is an important marine polysaccharide. Bacterial ulvan lyases play important roles in ulvan degradation and marine carbon cycling. Until now, only a small number of ulvan lyases have been characterized. Here, a new ulvan lyase, Uly1, belonging to polysaccharide lyase family 24 (PL24) from the marine bacterium Catenovulum maritimum, is characterized. The optimal temperature and pH for Uly1 to degrade ulvan are 40°C and pH 9.0, respectively. Uly1 degrades ulvan polysaccharides in the endolytic manner, mainly producing ΔRha3S, consisting of an unsaturated 4-deoxy-l-threo-hex-4-enopyranosiduronic acid and a 3-O-sulfated α-l-rhamnose. The structure of Uly1 was resolved at a 2.10-Å resolution. Uly1 adopts a seven-bladed β-propeller architecture. Structural and site-directed mutagenesis analyses indicate that four highly conserved residues, H128, H149, Y223, and R239, are essential for catalysis. H128 functions as both the catalytic acid and base, H149 and R239 function as the neutralizers, and Y223 plays a supporting role in catalysis. Structural comparison and sequence alignment suggest that Uly1 and many other PL24 enzymes may directly bind the substrate near the catalytic residues for catalysis, different from the PL24 ulvan lyase LOR_107, which adopts a two-stage substrate binding process. This study provides new insights into ulvan lyases and ulvan degradation.

Item Type: Article
Authors/Creators:Xu, F and Dong, F and Sun, X-H and Cao, H-Y and Fu, H-H and Li, C-Y and Zhang, X-Y and McMinn, A and Zhang, Y-Z and Wang, P and Chen, X-L
Keywords: ulvan, ulvan lyase, polysaccharide lyase family 24, marine bacterium, substrate recognition, catalytic mechanism
Journal or Publication Title: Applied and Environmental Microbiology
Publisher: American Society for Microbiology
ISSN: 1098-5336
DOI / ID Number: 10.1128/AEM.00412-21
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Copyright © 2021 American Society for Microbiology. All Rights Reserved.

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