Automated Docking to Explore Processivities of Family 6 Cellobiohydrolases and Endoglucanases

摘要

CELLOOLIGOSACCHARIDES WERE COMPUTATIONALLY DOCKED INTO THE ACTIVE SITES OF THE GLYCOSIDE HYDROLASE FAMILY 6 ENZYMES HYPO-CREA JECORINA (FORMERLY TRICHODERMA REESEI) CELLOBIOHYDROLASE AND THERMOBIFIDA FUSCA ENDOGLUCANASE. SUBSITE -2 EXERTS THE GREATEST INTERMOLECULAR ENERGY IN BINDING β-GLUCOSYL RESIDUES, WITH ENERGIES PROGRESSIVELY DECREASING TO EITHER SIDE. CUMULATIVE FORCES IMPARTING PROCESSIVITY ARE ALMOST AN ORDER OF MAGNITUDE LESS THAN FOR COMPARABLE ENZYMES IN GLYCOSIDE HYDROLASE FAMILY 7, CAUSED BY THE FEWER NUMBER OF MAIN SUBSITES IN FAMILY 6 ENZYMES. PUTATIVE SUBSITES -4, -3, +3, AND +4 EXIST IN H. JECORINA CELLOBIOHYDROLASE, BUT SUBSITES -4 AND +4 ARE OF MINOR IMPORTANCE IN T. FUSCA ENDOGLUCANASE. IN GENERAL, 2 TO 6 KCAL/MOL IS ADDED TO LIGAND INTERNAL ENERGIES BY THE TWISTING OF SCISSILE GLYCOSIDIC BONDS UPON BINDING. BINDING OF β-GLUCOSYL RESIDUES IN THE SKEW-BOAT CONFORMATION BY SUBSITE -1 OF CELLOTRIOSE AND LONGER SUBSTRATES ADDS ANOTHER 7 KCAL/MOL TO THEIR INTERNAL ENERGIES.