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Updated: May 30, 2026

Measurement of Fatty Acid β-Oxidation in a Suspension of Freshly Isolated Mouse Hepatocytes
Published on: September 9, 2021
Valproic acid utilizes the isoleucine breakdown pathway for its complete β-oxidation.
Paula B M Luís1, Jos P Ruiter, Rob Ofman
1Research Institute for Medicines and Pharmaceutical Sciences, iMed.UL, University of Lisbon, Lisbon, Portugal.
Valproic acid (VPA) interferes with isoleucine metabolism by inhibiting 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD). This study identifies MHBD and crotonase as key enzymes in VPA beta-oxidation and isoleucine breakdown.
Area of Science:
- Biochemistry
- Metabolic pathways
- Enzymology
Background:
- Valproic acid (VPA) is a widely used anticonvulsant with a growing range of therapeutic uses.
- The metabolic pathways of VPA and its interference with other metabolic processes are not fully understood.
Purpose of the Study:
- To elucidate the enzymatic basis for VPA's interference with isoleucine catabolism.
- To investigate the role of specific enzymes in the beta-oxidation pathway of VPA.
Main Methods:
- Gas chromatography/mass spectrometry (GC/MS) for urine organic acid analysis.
- In vitro enzymatic assays using heterologously expressed human 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD) and fibroblasts.
- Immunoprecipitation and activity assays for short-chain enoyl-CoA hydratase (ECHS1).
Main Results:
- Elevated urinary levels of 2-methyl-3-hydroxybutyric acid, an isoleucine metabolite, were observed in patients on VPA therapy.
- MHBD was confirmed to dehydrogenate 3-hydroxyvalproyl-CoA.
- MHBD activity was absent in patient fibroblasts when using 3-hydroxyvalproyl-CoA, and crotonase showed no hydratase activity with VPA-derived substrates.
Conclusions:
- MHBD is the sole enzyme responsible for the dehydrogenation of 3-hydroxyvalproyl-CoA.
- Crotonase (ECHS1) is the primary hydratase involved in VPA beta-oxidation, in addition to its role in isoleucine metabolism.
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