(a) Cytochrome c (red) is extracted from the aqueous phase (upper phase) into the ionic liquid phase (lower phase) through formation of a supramolecular complex with crown ethers. (b) Cytochrome c, which is an electron-transfer protein, cannot function as an enzyme. Cytochrome c in water displays minor peroxidase activity in the oxidation reaction of 2,6-dimethoxyphenol, whereas cytochrome c in the ionic liquid offers high peroxidase activity, and accelerates the oxidation reaction rate.