6ehn
Structural insight into a promiscuous CE15 esterase from the marine bacterial metagenome
Structural highlights
FunctionCE15_UNKP Displays some glucuronoyl esterase activity in vitro, since it is able to hydrolyze methyl 4-O-methyl-D-glucopyranosyluronate, allyl D-glucuronate, benzyl D-glucuronate and D-glucuronic acid methyl ester. However, esters of glucuronic acid are probably not its biological substrate, as they are not present in the marine environment. Can also hydrolyze a range of other esters, including p-nitrophenyl acetate. More likely biologically-relevant substrates for MZ0003 and other marine bacterial CE15s are algal cell wall polysaccharides, as these would be readily available in this environment and could be used as energy sources.[1] Publication Abstract from PubMedThe family 15 carbohydrate esterase (CE15) MZ0003, which derives from a marine Arctic metagenome, has a broader substrate scope than other members of this family. Here we report the crystal structure of MZ0003, which reveals that residues comprising the catalytic triad differ from previously-characterized fungal homologs, and resolves three large loop regions that are unique to this bacterial sub-clade. The catalytic triad of the bacterial CE15, which includes Asp 332 as its third member, closely resembles that of family 1 carbohydrate esterases (CE1), despite the overall lower structural similarity with members of this family. Two of the three loop regions form a subdomain that deepens the active site pocket and includes several basic residues that contribute to the high positive charge surrounding the active site. Docking simulations predict specific interactions with the sugar moiety of glucuronic-acid substrates, and with aromatically-substituted derivatives that serve as model compounds for the lignin-carbohydrate complex of plant cell walls. Molecular dynamics simulations indicate considerable flexibility of the sub-domain in the substrate-bound form, suggesting plasticity to accommodate different substrates is possible. The findings from this first reported structure of a bacterial member of the CE15 family provide insight into the basis of its broader substrate specificity. Structural insight into a CE15 esterase from the marine bacterial metagenome.,De Santi C, Gani OA, Helland R, Williamson A Sci Rep. 2017 Dec 8;7(1):17278. doi: 10.1038/s41598-017-17677-4. PMID:29222424[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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