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Publication Abstract from PubMed

The glycoside hydrolase family 20 (GH20) predominantly features N-acetylhexosaminidases (EC 3.2.1.52), with only few known lacto-N-biosidases (EC 3.2.1.140; LNBases). LNBases catalyze the degradation of lacto-N-tetraose (LNT), a prominent component of human milk oligosaccharides, thereby supporting a healthy infant gut microbiome development. We investigated GH20 diversity to discover novel enzymes that release disaccharides such as lacto-N-biose (LNB). Our approach combined peptide clustering, sequence analysis, and 3D structure model evaluation to assess active site topologies, focusing on the presence of a subsite -2. Five LNBases were active on pNP-LNB and four showed activity on LNT. One enzyme displayed activity on both pNP-LacNAc and pNP-LNB, establishing the first report of N-acetyllactosaminidase (LacNAcase) activity. Exploration of this enzyme cluster led to the identification of four additional enzymes sharing this dual substrate specificity. Comparing the determined crystal structure of a specific LNBase (TrpyGH20) and the first crystal structure of an enzyme with dual LacNAcase/LNBase activity (TrdeGH20) revealed a highly conserved subsite -1, common to GH20 enzymes, while the -2 subsites varied significantly. TrdeGH20 had a wider subsite -2, accommodating Gal with both beta1,4- and beta1,3-linkages to the GlcNAc in subsite -1. Biotechnological applications of these enzymes may include structural elucidation of complex carbohydrates and glycoengineering.

Discovery of Lacto-N-biosidases and a Novel N-Acetyllactosaminidase Activity in the CAZy Family GH20: Functional Diversity and Structural Insights.,Vuillemin M, Muschiol J, Zhang Y, Holck J, Barrett K, Morth JP, Meyer AS, Zeuner B Chembiochem. 2024 Sep 6:e202400710. doi: 10.1002/cbic.202400710. PMID:39239753^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.