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Mechanistic insights into substrate recognition and catalysis of a new ulvan lyase of polysaccharide lyase family 24
journal contribution
posted on 2023-05-21, 01:05 authored by Xu, F, Dong, F, Sun, X-H, Cao, H-Y, Fu, H-H, Li, C-Y, Zhang, X-Y, Andrew McMinnAndrew McMinn, Zhang, Y-Z, Wang, P, Chen, X-LUlvan 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.
History
Publication title
Applied and Environmental MicrobiologyVolume
87Issue
12Article number
e00412-21Number
e00412-21Pagination
1-13ISSN
1098-5336Department/School
Institute for Marine and Antarctic StudiesPublisher
American Society for MicrobiologyPlace of publication
United StatesRights statement
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