Structure and biochemical properties of the alkene producing cytochrome P450 OleTJE (CYP152L1) from the Jeotgalicoccus sp. 8456 bacterium.

The production of hydrocarbons in nature has been documented for only a limited set of organisms, with many of the molecular components underpinning these processes only recently identified. There is an obvious scope for application of these catalysts and engineered variants thereof in the future production of biofuels. Here we present biochemical characterization and crystal structures of a cytochrome P450 fatty acid peroxygenase: the terminal alkene forming OleTJE (CYP152L1) from Jeotgalicoccus sp. 8456. OleTJE is stabilized at high ionic strength, but aggregation and precipitation of OleTJE in low salt buffer can be turned to advantage for purification, because resolubilized OleTJE is fully active and extensively dissociated from lipids. OleTJE binds avidly to a range of long chain fatty acids, and structures of both ligand-free and arachidic acid-bound OleTJE reveal that the P450 active site is preformed for fatty acid binding. OleTJE heme iron has an unusually positive redox potential (-103 mV versus normal hydrogen electrode), which is not significantly affected by substrate binding, despite extensive conversion of the heme iron to a high spin ferric state. Terminal alkenes are produced from a range of saturated fatty acids (C12-C20), and stopped-flow spectroscopy indicates a rapid reaction between peroxide and fatty acid-bound OleTJE (167 s(-1) at 200 µm H2O2). Surprisingly, the active site is highly similar in structure to the related P450BSß, which catalyzes hydroxylation of fatty acids as opposed to decarboxylation. Our data provide new insights into structural and mechanistic properties of a robust P450 with potential industrial applications.

Human P450-like oxidation of diverse proton pump inhibitor drugs by 'gatekeeper' mutants of flavocytochrome P450 BM3.

Production of drug metabolites is one area where enzymatic conversion has significant advantages over synthetic chemistry. These high value products are complex to synthesize, but are increasingly important in drug safety testing. The vast majority of drugs are metabolized by cytochromes P450 (P450s), with oxidative transformations usually being highly regio- and stereo-selective. The PPIs (proton pump inhibitors) are drugs that are extensively metabolized by human P450s, producing diverse metabolites dependent on the specific substrate. In the present paper we show that single mutations (A82F and F87V) in the biotechnologically important Bacillus megaterium P450 BM3 enzyme cause major alterations in its substrate selectivity such that a set of PPI molecules become good substrates in these point mutants and in the F87V/A82F double mutant. The substrate specificity switch is analysed by drug binding, enzyme kinetics and organic product analysis to confirm new activities, and X-ray crystallography provides a structural basis for the binding of esomeprazole to the F87V/A82F enzyme. These studies confirm that such 'gatekeeper' mutations in P450 BM3 produce major perturbations to its conformation and substrate selectivity, enabling novel P450 BM3 reactions typical of those performed by human P450s. Efficient transformation of several PPI drugs to human-like products by BM3 variants provides new routes to production of these metabolites.

Multidimensional on-line screening for ligands to the alpha3beta4 neuronal nicotinic acetylcholine receptor using an immobilized nicotinic receptor liquid chromatographic stationary phase.

The alpha3beta4 subtype of the neuronal nicotinic acetylcholine receptor (nAChR) subtype was immobilized on a liquid chromatographic support and the resulting column used for the rapid and direct on-line screening for nAChR ligands. A multidimensional chromatographic system was developed consisting of the immobilized receptor column (NR column) connected via a switching valve to a C(18) column that was, in turn, connected to a single quadrupole mass spectrometer. A mixture of 18 compounds, containing alpha3beta4 nAChR (7) and compounds that are not alpha3beta4 nAChR ligands (11), was injected onto the NR column. The mobile phase consisted of ammonium acetate (10 mM, pH 7.4)-methanol (95:5, v/v) and the flow-rate was 0.2 ml/min. For the first 8 min the eluent was directed to waste. At t=8 min, the switching valve was rotated and the NR column connected to the C(18) column. The eluent from the NR column was directed to the C(18) column for 12 min. At t=20 min, the switching valve was rotated and the NR column was disconnected from the C(18) column. The compounds trapped on the C(18) column were separated and eluted onto the mass spectrometer using a mobile phase of ammonium acetate (10 mM, pH 7.4)-methanol (40:60, v/v) at a flow-rate of 1.0 ml/min. Detection was accomplished using total ion monitoring. The multidimensional system correctly isolated six of the seven alpha3beta4 nAChR ligands and only one of the 11 non-ligands was found with the alpha3beta4 nAChR ligands. The results indicate that the multidimensional liquid chromatographic system can be used for the on-line screening of chemical mixtures for alpha3beta4 nAChR ligands.