8tse
Crystal structure of a CE15 glucuronoyl esterase from Ruminococcus flavefaciens
Structural highlights
FunctionCESA_RUMFL Esterase involved in the degradation of plant cell wall polysaccharides. Catalyzes the deacetylation of chemically acetylated xylan and native, steam-extracted xylan (PubMed:10846217). Seems to act in synergy with the xylanase XynD which produces xylo-oligosaccharides (PubMed:10846217). Also catalyzes the deesterification of methyl esters of 4-O-methyl-D-glucuronic acid (MeGlcA) side residues in synthetic glucuronoxylan methyl ester, suggesting that it may be able to cleave ester linkages between MeGlcA carboxyl and more complex alcohols, including linkages between hemicellulose and lignin alcohols in plant cell walls (PubMed:26216754).[1] [2] Publication Abstract from PubMedGlucuronoyl esterases (GEs) are carbohydrate active enzymes in carbohydrate esterase family 15 which are involved in the hydrolysis of lignin-carbohydrate complexes. They are encoded by a wide range of aerobic and anaerobic fungi and bacteria inhabiting diverse environments. The rumen microbiome is a complex microbial community with a wide array of enzymes that specialize in deconstructing plant cell wall carbohydrates. Enzymes from the rumen tend to show low similarity to homologues found in other environments, making the rumen microbiome a promising source for the discovery of novel enzymes. Using a combination of phylogenetic and structural analysis, we investigated the structure-function relationship of GEs from the rumen bacteria Fibrobacter succinogenes and Ruminococcus flavefaciens, and from the rumen fungus, Piromyces rhizinflata. All adopt a canonical alpha/beta hydrolase fold and possess a structurally conserved Ser-His-Glu/Asp catalytic triad. Structural variations in the enzymes are localized to loops surrounding the active site. Analysis of the active site structures in these enzymes emphasized the importance of structural plasticity in GEs with non-canonical active site conformations. We hypothesize that interkingdom HGT events may have contributed to the diversity of GEs in the rumen, and this is demonstrated by the phylogenetic and structural similarity observed between rumen bacterial and fungal GEs. This study advances our understanding of the structure-function relationship in glucuronoyl esterases and illuminates the evolutionary dynamics that contribute to enzyme diversity in the rumen microbiome. Structural, Biochemical, and Phylogenetic Analysis of Bacterial and Fungal Carbohydrate Esterase Family 15 Glucuronoyl Esterases in the Rumen.,Gruninger RJ, Kevorkova M, Low KE, Jones DR, Worrall L, McAllister TA, Abbott DW Protein J. 2024 Aug;43(4):910-922. doi: 10.1007/s10930-024-10221-0. Epub 2024 Aug , 17. PMID:39153129[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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