8oi4

Publication Abstract from PubMed

Polysaccharide Utilization Loci (PULs) are physically linked gene clusters conserved in the Gram-negative phylum of Bacteroidota and are valuable sources for Carbohydrate Active enZyme (CAZyme) discovery. This study focuses on BD-beta-Gal, an enzyme encoded in a metagenomic PUL and member of the Glycoside Hydrolase family 154 (GH154). BD-beta-Gal showed exo-beta-galactosidase activity with regiopreference for hydrolyzing beta-d-(1,6) glycosidic linkages. Notably, it exhibited a preference for d-glucopyranosyl (d-Glcp) over d-galactopyranosyl (d-Galp) and d-fructofuranosyl (d-Fruf) at the reducing end of the investigated disaccharides. In addition, we determined the high resolution crystal structure of BD-beta-Gal, thus providing the first structural characterization of a GH154 enzyme. Surprisingly, this revealed an (alpha/alpha)(6) topology, which has not been observed before for beta-galactosidases. BD-beta-Gal displayed low structural homology with characterized CAZymes, but conservation analysis suggested that the active site was located in a central cavity, with conserved E73, R252, and D253 as putative catalytic residues. Interestingly, BD-beta-Gal has a tetrameric structure and a flexible loop from a neighboring protomer may contribute to its reaction specificity. Finally, we showed that the founding member of GH154, BT3677 from Bacteroides thetaiotaomicron, described as beta-glucuronidase, displayed exo-beta-galactosidase activity like BD-beta-Gal but lacked a tetrameric structure.

Novel beta-galactosidase activity and first crystal structure of Glycoside Hydrolase family 154.,Hameleers L, Pijning T, Gray BB, Faure R, Jurak E N Biotechnol. 2023 Dec 30;80:1-11. doi: 10.1016/j.nbt.2023.12.011. PMID:38163476^[1]

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