title: Hydrogen location in stages of an enzyme-catalyzed reaction: time-of-flight neutron structure of D-xylose isomerase with bound D-xylulose.
abstract: 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 C1 and C2, the molecular site of isomerization of xylose. These findings impact our understanding of the reaction mechanism.
authors.affiliation: M888, Bioscience Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Andrey Y
authors.initials: AY
authors.lastname: Kovalevsky
authors.forename: Amy K
authors.initials: AK
authors.lastname: Katz
authors.forename: H L
authors.initials: HL
authors.lastname: Carrell
authors.forename: Leif
authors.initials: L
authors.lastname: Hanson
authors.forename: Marat
authors.initials: M
authors.lastname: Mustyakimov
authors.forename: S Zoe
authors.initials: SZ
authors.lastname: Fisher
authors.forename: Leighton
authors.initials: L
authors.lastname: Coates
authors.forename: Benno P
authors.initials: BP
authors.lastname: Schoenborn
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: Bunick
authors.forename: Jenny P
authors.initials: JP
authors.lastname: Glusker
authors.forename: Paul
authors.initials: P
authors.lastname: Langan
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry*; D015394:Molecular Structure; D009502:Neutrons; D011485:Protein Binding; D014996:Xylulose / Q000737:chemistry* / Q000378:metabolism
chemical_list: D014996:Xylulose; D006859:Hydrogen; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase