Kinetic and spectroscopic studies of N694C lipoxygenase: a probe of the substrate activation mechanism of a nonheme ferric enzyme.

ABSTRACT: Lipoxygenases (LOs) comprise a class of substrate activating mononuclear nonheme iron enzymes which catalyze the hydroperoxidation of unsaturated fatty acids. A commonly proposed mechanism for LO catalysis involves H-atom abstraction by an FeIII-OH- site, best described as a proton coupled electron transfer (PCET) process, followed by direct reaction of O2 with the resulting substrate radical to yield product. An alternative mechanism that has also been discussed involves the abstraction of a proton from the substrate by the FeIII-OH leading to a sigma-organoiron intermediate, where the subsequent sigma bond insertion of dioxygen into the C-Fe bond completes the reaction. H-atom abstraction is favored by a high E(o) of the FeII/FeIII couple and high pK(a) of water bound to the ferrous stat

SUBMITTER: Neidig ML 

PROVIDER: S-EPMC2896304 | biostudies-literature | 2007 Jun

REPOSITORIES: biostudies-literature