Catalytic strategy for carbon-carbon bond scission by the cytochrome P450 OleT.

Abstract

OleT is a cytochrome P450 that catalyzes the hydrogen peroxide-dependent metabolism of Cn chain-length fatty acids to synthesize Cn-1 1-alkenes. The decarboxylation reaction provides a route for the production of drop-in hydrocarbon fuels from a renewable and abundant natural resource. This transformation is highly unusual for a P450, which typically uses an Fe(4+)-oxo intermediate known as compound I for the insertion of oxygen into organic substrates. OleT, previously shown to form compound I, catalyzes a different reaction. A large substrate kinetic isotope effect (≥8) for OleT compound I decay confirms that, like monooxygenation, alkene formation is initiated by substrate C-H bond abstraction. Rather than finalizing the reaction through rapid oxygen rebound, alkene synthesis proceeds through the formation of a reaction cycle intermediate with kinetics, optical properties, and reactivity indicative of an Fe(4+)-OH species, compound II. The direct observation of this intermediate, normally fleeting in hydroxylases, provides a rationale for the carbon-carbon scission reaction catalyzed by OleT.