Biochemical and structural investigation of the CE15 family: Glucuronoyl esterases acting on recalcitrant biomass

Glucuronoyl esterases (GEs) are a relatively new class of enzymes which cleave ester linkages between lignin and glucuronoxylan. GEs have been identified in many biomass-degrading microbes and are now classified into the Carbohydrate Esterase Family 15 (CE15). The CE15 family is diverse (as low as 20% sequence identity), however to-date only a few GEs from a small clade of the CE15 phylogenetic tree have been biochemically characterized and only two protein structures have been solved. To investigate the diversity of CE15 members, we have studied a broad range of proteins from across the phylogenetic tree. Enzymes were biochemically characterized and three-dimensional structures for two of the enzymes were solved. Analysis of the structures suggest possible binding sites for lignin fragments and xylooligosaccharides that have not been previously reported. Investigations into the molecular determinants supporting the potential binding sites is being pursued.