The Song Remains the Same, but the Enzymes Don’t: Imidazolium ILs as Potential Disruptors of Fatty Acid Metabolism

This study examined twenty-eight N-methylimidazolium ionic liquids (ILs) with various substituents and anions to assess their impact on the activity of Carnitine Acetyltransferase (CAT), an indispensable enzyme in human metabolism. In vitro experiments demonstrated that these compounds inhibited CAT in a concentration-dependent manner, with IC50 values ranging from 0.93 to 30.8 mM. Structural analysis of the ILs revealed the following structure–activity relationships: (i) the length of the hydrocarbon chain at N3 markedly affects CAT activity, with longer chains resulting in stronger inhibition; (ii) the degree of unsaturation and the presence of polar groups are not essential for increased activity; (iii) the effect of the anion aligns with the Hofmeister series. One of the most potent compounds, 1-decyl-3-methylimidazolium bromide [C10C1im]Br, was identified as a mixed inhibitor of CAT with a Ki of 0.77 mM. These findings raise concerns about the biocompatibility of commonly used imidazolium ILs, as they may interfere with fatty acid oxidation by inhibiting their cellular transport.