Origin of the Regioselective Fatty-Acid Hydroxylation versus Decarboxylation by a Cytochrome P450 Peroxygenase: What Drives the Reaction to Biofuel Production?

Abstract

The cytochromes P450 are heme-based mono-oxygenases or peroxygenases involved in vital reaction processes for human health. A recently described P450 per-oxygenase, OleTJE , converts long-chain fatty acids to terminal olefins and as such may have biotechnological relevance in biodiesel production. However, the reaction produces significant amounts of α- and β-hydroxylation by-products, and their origin are poorly understood. Herein, we elucidate through a QM/MM study on the bifurcation pathways how the three possible products are generated and show how the enzyme can be further engineered for optimum desaturase activity. The studies showed that the polarity and the solvent accessibility of the substrate in the binding pocket destabilize the OH-rebound pathways and kinetically enable a thermodynamically otherwise unfavorable decarboxylation reaction. The origins of the bifurcation pathways are analyzed with valence-bond models that highlight the differences in reaction mechanism.

Keywords: bioengineering; cytochromes; density functional calculations; heme proteins; iron.