Metabolomics reveals that carnitine palmitoyltransferase‐1 is a novel target for oxidative inactivation in human cells

Oxidative dysfunction in the metabolism has long been implicated in diverse biological disorders. Although a substantial number of metabolic enzymes are targeted for inactivation by oxidative stress, identifying those targets remains difficult due to a lack of comprehensive observations of the metabolism acting through the stress response. We herein developed a metabolomics strategy using integrative liquid chromatography‐mass spectrometry (LC‐MS) and observing rapid metabolomic changes in response to hydrogen peroxide (H₂O₂)‐induced oxidative stress in HeLa cells. Among the many metabolite changes detected, the most characteristic metabolites uniquely indicated carnitine palmitoyltransferase‐1 (CPT1), the critical enzyme for mitochondrial β‐oxidation of long‐chain fatty acids, to be a target for oxidative inactivation. We showed that the enzymatic activity of CPT1 significantly declined by H₂O₂ in several human cells. Interestingly, the inactivation was shown to be a direct effect of H₂O₂ in vitro, but substantially occurred when cells were cultured with some reagents that generate reactive oxygen species (ROS). Thus, our results suggest the generality of CPT1 inhibition under various stress conditions associated with ROS generation, providing an insight into a mechanism for oxidative dysfunction in mitochondrial metabolism. Our metabolome data additionally suggest that certain methyltransferase(s) may be targets of oxidative stress as well.