Q. Wan, J. Parks, B. L Hanson, S. Z Fisher, A. Ostermann, T. E Schrader, D. E Graham, L. Coates, P. Langan, and A. Kovalevsky
Direct Determination of Protonation States and Visualization of Hydrogen Bonding in a Glycoside Hydrolase with Neutron Crystallography
Proceedings of the National Academy of Sciences of the United States of America, 112(40):12384–12389.
Most enzymatic reactions involve hydrogen or proton transfer among the enzyme, substrate, and water at physiological pH. Thus, enzyme catalysis cannot be fully understood without accurate mapping of hydrogen atom positions in these macromolecular catalysts. Direct information on the location of hydrogen atoms can be obtained using neutron crystallography. We used neutron crystallography and biomolecular simulation to characterize the initial stage of the glycoside hydrolysis reaction catalyzed by a family 11 glycoside hydrolase. We provide evidence that the catalytic glutamate residue alternates between two conformations bearing different basicities, first to obtain a proton from the bulk solvent, and then to deliver it to the glycosidic oxygen to initiate the hydrolysis reaction.