title: An investigation into the butyrylcholinesterase-catalyzed hydrolysis of formylthiocholine using heavy atom kinetic isotope effects.
abstract: Heavy atom kinetic isotope effects (KIEs) were determined for the butyrylcholinesterase-catalyzed hydrolysis of formylthiocholine (FTC). The leaving-S, carbonyl-C, and carbonyl-O KIEs are (34)k=0.994±0.004, (13)k=1.0148±0.0007, and (18)k=0.999±0.002, respectively. The observed KIEs support a mechanism for both acylation and deacylation where the steps up to and including the formation of the tetrahedral intermediate are at least partially rate determining. These results, in contrast to previous studies with acetylthiocholine, suggest that the decomposition of a tetrahedral intermediate is not rate-determining for FTC hydrolysis. Structural differences between the two substrates are likely responsible for the observed mechanism change with FTC.
authors.affiliation: California Polytechnic State University, San Luis Obispo, CA 93407, United States.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Fogle
authors.affiliation: California Polytechnic State University, San Luis Obispo, CA 93407, United States.
authors.forename: John F
authors.initials: JF
authors.lastname: Marlier
authors.affiliation: University of Washington Bothell, Bothell, WA 98011, United States.
authors.forename: Anthony
authors.initials: A
authors.lastname: Stillman
authors.affiliation: University of Washington Bothell, Bothell, WA 98011, United States.
authors.forename: Xin
authors.initials: X
authors.lastname: Gao
authors.affiliation: University of Washington Bothell, Bothell, WA 98011, United States.
authors.forename: Yashas
authors.initials: Y
authors.lastname: Rao
authors.affiliation: University of Washington Bothell, Bothell, WA 98011, United States. Electronic address: lrobins@uw.edu.
authors.forename: Lori I
authors.initials: LI
authors.lastname: Robins
mesh_terms: D055162:Biocatalysis; D002091:Butyrylcholinesterase / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007554:Isotopes / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D015394:Molecular Structure; D013860:Thiocholine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism
chemical_list: D007554:Isotopes; C000612180:formylthiocholine; D013860:Thiocholine; D002091:Butyrylcholinesterase
keywords: Butyrylcholinesterase; Kinetic isotope effects; Thioester hydrolysis