Ionic liquid effects on the activity of monooxygenase P450 BM-3

Abstract

P450 monooxygenases oxidize a broad range of substrates including fatty acids, alcohols, aliphatic and aromatic hydrocarbons which are often poorly soluble in water and have K_m values in the millimolar range. Cosolvent and host–guest chemistry have thus been supplemented to increase catalytic efficiencies. Ionic liquids are alternative solvents and cosolvents in biocatalysis and have received an escalating interest due to unique properties such as tunable hydrophobicity and hydrophilicity. Effects of ten ionic liquids on cytochrome P450 BM-3 activity were investigated by evaluating the influence of hydrophobicity and ion pairs on P450 BM-3. Investigated ionic liquids comprised a range of four anions, four 1-alkyl-3-methylimidazolium derivatives differing in hydrophobic chain length, two altered head groups (pyridinium and pyrrolidinium) and an additional functional group in the side chain (nitrile). Results indicate that varying the chain length of the 1-alkyl-3-methylimidazolium has apparent effects on the resistance of P450 BM-3 (based on EC₅₀), with increasing inhibition in the order of EMIM Cl (232 ± 8) > BMIM Cl (148 ± 5) > HMIM Cl (32 ± 2) > OMIM Cl (9 ± 1).