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Kovalevsky AY , Katz AK , Carrell HL , Hanson L , Mustyakimov M , Fisher SZ , Coates L , Schoenborn BP , Bunick GJ , Glusker JP , Langan P
Hydrogen location in stages of an enzyme-catalyzed reaction: Time-of-flight neutron structure of D-xylose isomerase with bound D-xylulose
Biochemistry. 2008 Jul;47(29) :7595-7597
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The time-of-flight neutron Laue technique has been used to determine the location of hydrogen atoms in the enzyme D-xylose isomerase (XI). The neutron structure of crystalline XI with bound product, D-xylulose, shows, unexpectedly, that O5 Of D-xylulose is not protonated but is hydrogen-bonded to doubly protonated His54. Also, Lys289, which is neutral in native XI, is protonated (positively charged), while the catalytic water in native XI has become activated to a hydroxyl anion which is in the proximity of Cl and C2, the molecular site of isomerization of xylose. These findings impact our understanding of the reaction mechanism.
Kovalevsky, Andrey Y. Katz, Amy K. Carrell, H. L. Hanson, Leif Mustyakimov, Marat Fisher, S. Zoe Coates, Leighton Schoenborn, Benno P. Bunick, Gerard J. Glusker, Jenny P. Langan, Paul AMER CHEMICAL SOC