Modeling temperature dependent kinetic isotope effects for hydrogen transfer in a series of soybean lipoxygenase mutants: The effect of anharmonicity upon transfer distance.

ABSTRACT: Soybean lipoxygenase-1 (SLO) catalyzes the oxidation of linoleic acid. The rate-limiting step in this transformation is the net abstraction of the pro-S hydrogen atom from the center of the 1,5-pentadienyl moiety in linoleic acid. The large deuterium kinetic isotope effect (KIE) for this step appears in the first order rate constant ((D)k(cat) = 81 ± 5 at T = 25 °C). Furthermore, the KIE and the rate for protium abstraction are weakly temperature dependent (E(A,D) - E(A,H) = 0.9 ± 0.2 kcal/mol and E(A,H) = 2.1 ± 0.2 kcal/mol, respectively). Mutations at a hydrophobic site about 13 Å from the active site Fe(III), Ile(553), induce a marked temperature dependence that varies roughly in accordance with the degree to which the residue is changed in bulk from the wild type Ile. While the tempera

SUBMITTER: Meyer MP 

PROVIDER: S-EPMC2995544 | biostudies-literature | 2005 Dec

REPOSITORIES: biostudies-literature