22 September 2020: Like PLs, but different:
We are happy to announce the completion of a new Lexicon
page on Polysaccharide epimerases
today. Margrethe Gaardlos
spearheaded the composition of this new page, with input from co-author Anne Tøndervik
and Responsible Curator Finn Lillelund Aachmann
. Although they are not categorized into families in the CAZy system, Polysaccharide epimerases
bear a lot of structural and mechanistic similarity to Polysaccharide Lyases
: Instead of catalyzing an elimination reaction to break poly-uronic acid chains, Polysaccharide epimerases
simply use the first part of the PL
mechanism to remove and re-add the C-5 proton. The resulting change in the configuration of the C-6 carboxylate has major impacts on polysaccharide structure and properties. The Norwegian team has done a tremendous job in capturing the broad history of these enzymes, including their diverse substrate specificities and structures (and over 130 references!), which you can read all about here.
(We also thank Mirjam Czjzek
for championing the inclusion of the "PEs" in CAZYpedia
6 August 2020: A beta-1,3-glucanase family with a deep history: Julie Grondin's Glycoside Hydrolase Family 81 page was Curator Approved by Al Boraston today. GH81 has a long history of discovery and mechanistic study, including by original CAZypedian and Cellulase/CAZyme GRC co-founder David Wilson and co-workers. By capturing a phenomenal number of oligosaccharide complexes, Al's group has recently provided detailed molecular description of how enzymes in this family specifically recognize the helical structure adopted by beta-1,3-glucans. Be sure to check out the GH81 page to get the full history of the contributions of a number of groups world-wide to our knowledge of this family.
23 July 2020: Another CE family page from our friends at WLU! The Carbohydrate Esterase Family 7 page was finalized and promoted to Curator Approved status today. Joel Weadge and Michael Suits have been leading the completion of a bunch of CE pages with the help of keen students from Wilfred Laurier University (see CE3, CE4, and CE9). This time, Emily Rodriguez produced the CE7 page, which encompasses acetyl xylan esterases and cephalosporin-C deacetylases. Learn more about the specificity, mechanism, and three-dimensional structure of CE7 enzymes here.
19 June 2020: Three additional alginate lyase families! The number of PL family pages in CAZypedia continues to grow with the promotion of the Polysaccharide Lyase Family 6, Polysaccharide Lyase Family 15, and Polysaccharide Lyase Family 17 pages to Curator Approved status today. We thank Emil G.P. Stender for his hard work in tackling this trifecta of bacterial alginate lyase families (including some heparin/heparan sulfate lyases from the human gut microbiota in PL15), which were vetted Responsible Curator Birte Svensson. Dig into the details of these families on the PL6, PL15, and PL17 pages, in comparison with the recently completed PL7 page (see previous news item, below).
17 June 2020: PLs from the sea. The Polysaccharide Lyase Family 7 page, which was written by Nadine Gerlach, was promoted to completed by Curator Approved status today by Jan-Hendrik Hehemann. The founding member of PL7, an alginate lyase, was characterized way back in 1993 by a team notably including CAZypedian Gurvan Michel. Alginate is heteropolysaccharide from brown algae and mucoid bacteria, consisting of beta-d-mannuronate (M) and alpha-l-guluronate (G) residues in varying ratios and intra-chain distributions, depending on the source. As a result, PL7 members exhibit mannuronate, guluronate, or mixed link specificity. Read more about the deep history of enzymolgoy and structural biology of PL7 here, including seminal work by Jan-Hendrik showing the horizontal gene transfer of these enzymes into the human gut microbiota and other marine bacteria.
16 June 2020: From rotting plants to vegetable digestion in the gut. The Polysaccharide Lyase Family 9 page was completed by Ana Luis and upgraded to Curator Approved status today by Wade Abbott. PL9 was originally identified and characterized as part of the pectin-degrading machinery from the plant pathogenic bacterium Dickeya dadantii (Erwinia chrysanthemi), including seminal structural work by Richard Pickersgill and colleagues. More recently Ana and Wade, as part of a big team involving other CAZypedians Jonathon Briggs, Didier Ndeh, Alan Cartmell, Bernard Henrissat, and Harry Gilbert, shed new light on the role of PL9 members in the human gut microbiota. Take some time to learn more about the long and rich history of Polysaccharide Lyase Family 9!
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