Selective Hydrolysis\nof Heterooligosaccharides by\nPoly(acrylate) Gel Catalysts

Natural glycoside hydrolases are distinguished by their\nability\nto hydrolyze glycosidic bonds with high efficiency and selectivity.\nThis feature is achieved through specific interactions in the active\nsite during catalytic turnover and is not just facilitated by two\ncatalytically active amino acids. Intrigued by these features, a biomimetic\nα-galactosidase mimic was developed using an empirical catalyst\ndesign. Starting with a library of 704 gels of which 250 have a unique\ncomposition synthesized from TEGDMA cross-linker and 7 selected monomers,\n238 monomodal gels are evaluated for their ability to hydrolyze the\n1→6 α-glycosidic bond in the disaccharide melibiose.\nAmong those, 13 polyacrylate gels with the potential for high catalytic\nactivity are identified using spectrophotometric screening assays\nbased on Schiff bases formed with toluidine. The best-performing polyacrylate\n(gel A) was found to have a 1500-fold higher proficiency to hydrolyze\nthe 1→6 α-glycosidic bond in melibiose over the 1→2\nα-glycosidic bond in sucrose, translating to selective hydrolysis\nof the glycosidic linkages in the trisaccharide raffinose. The matrix\nof gel A is composed of 25 mol % TEGDMA cross-linker and equimolar\namounts of cyclohexyl, butyl, and benzyl acrylate accounting for CH-π\nand hydrophobic interaction in the surrounding of a hydrolytic binuclear\nCu(II) complex. The combined observations underline a paramount influence\nof matrix-stabilizing effects on the transition state of the hydrolysis\nof glycosidic bonds and may pave the way for the rapid development\nof catalysts transforming biomass.