Important hydrogenbonding interactions between substrate OH-groups inyeasta-glucosidases andoligo-1,6-glucosidase from glycoside hydrolase family 13 have been identi®ed by measuring the rates of hydrolysis of methyla-isomaltoside and its seven monodeoxygenated analogs. The transition-state stabilization energy, DDGà, contributed by the indi-vidual OH-groups was calculated from the activities for the parent and the deoxy analogs, respectively, according toDDGà ±RTln[(Vmax/Km)analog /(Vmax/Km) parent]
