Comparison of peroxidase activities of hemin, cytochrome c and microperoxidase-11 in molecular solvents and imidazolium-based ionic liquids

• Published in: Journal of molecular catalysis. B, Enzymatic Vol. 18; no. 1; pp. 109 - 120
• Main Authors: Laszlo, Joseph A, Compton, David L
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 13.09.2002; Elsevier Science
• Subjects: Biocatalysis; Biological and medical sciences; Biotechnology; Cytochrome c; Enzyme engineering; Fundamental and applied biological sciences. Psychology; Ionic liquids; Methods. Procedures. Technologies; Miscellaneous; Non-aqueous media; Oxidoreductase; Cytochrome c; Ionic liquids; Non-aqueous media; Biocatalysis; Oxidoreductase; Enzyme; Ligand; Ionic solution; Electrocatalysis; Biological fixation; Guaiacol; Non aqueous solution; Hemin; Protoporphyrin; Enzymatic activity; Peroxidases; Oxidation; Kinetics; Oxidoreductases; Comparative study
• ISSN: 1381-1177; 1873-3158
• DOI: 10.1016/S1381-1177(02)00074-7

The ability of Fe(III)protoporphyrin(IX) chloride (hemin), microperoxidase-11 (MP-11), and cytochrome c (cyt- c) to oxidize 2-methoxyphenol (guaiacol) was examined in the room-temperature ionic liquids (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf 2N]) and the hexafluorophosphates of 1-butyl- and 1-octyl-3-methylimidazolium, ([bmim][PF 6] and [omim][PF 6]), respectively. All three biocatalysts displayed peroxidase activity when activated by an electron acceptor, tert-butyl hydroperoxide for hemin and hydrogen peroxide for MP-11 and cyt- c. Hemin required the addition of a coordinating base, pyridine or N-methylimidazole (NMI), to produce an active complex. Cyt- c did not require exogenous ligands for activity in IL, although their addition increased peroxidase activity. MP-11 could not be solubilized without an exogenous ligand, therefore, whether MP-11 was active in the absence of such ligands was not determined. Pyridine provided higher activities than NMI for the three catalysts. Hemin and MP-11 peroxidase activities were markedly higher in IL compared to molecular solvents of similar polarity, as characterized by probe solvatochromic behavior, while cyt- c activity was comparable between both types of solvents. There was no consistent preference by the catalysts for a particular IL. These observations indicate that IL are suitable media for bioelectrocatalysis.