Investigating inner-sphere reorganization via secondary kinetic isotope effects in the C-H cleavage reaction catalyzed by soybean lipoxygenase: tunneling in the substrate backbone as well as the transferred hydrogen.

ABSTRACT: This work describes the application of NMR to the measurement of secondary deuterium (2° (2)H) and carbon-13 ((13)C) kinetic isotope effects (KIEs) at positions 9-13 within the substrate linoleic acid (LA) of soybean lipoxygenase-1. The KIEs have been measured using LA labeled with either protium (11,11-h2-LA) or deuterium (11,11-d2-LA) at the reactive C11 position, which has been previously shown to yield a primary deuterium isotope effect of ca. 80. The conditions of measurement yield the intrinsic 2° (2)H and (13)C KIEs on k(cat)/K(m) directly for 11,11-d2-LA, whereas the values for the 2° (2)H KIEs for 11,11-h2-LA are obtained after correction for a kinetic commitment. The pattern of the resulting 2° (2)H and (13)C isotope effects reveals values that lie far above those predicted from

SUBMITTER: Meyer MP 

PROVIDER: S-EPMC3090704 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature