Mitochondrial metabolism of valproic acid.
The beta-oxidation of valproic acid (2-propylpentanoic acid), an anticonvulsant drug with hepatotoxic side effects, was studied with subcellular fractions of rat liver and with purified enzymes of beta-oxidation. 2-Propyl-2-pentenoyl-CoA, a presumed intermediate in the beta-oxidation of valproic acid, was chemically synthesized and used to demonstrate that enoyl-CoA hydratase or crotonase catalyzes its hydration to 3-hydroxy-2-propylpentanoyl-CoA. The latter compound was not acted upon by soluble L-3-hydroxyacyl-CoA dehydrogenases from mitochondria or peroxisomes but was dehydrogenated by an NAD(+)-dependent dehydrogenase associated with a mitochondrial membrane fraction. The product of the dehydrogenation, presumably 3-keto-2-propylpentanoyl-CoA, was further characterized by fast bombardment mass spectrometry. 3-Keto-2-propylpentanoyl-CoA was not cleaved thiolytically by 3-ketoacyl-CoA thiolase or a mitochondrial extract but was slowly degraded, most likely by hydrolysis. The availability of 2-propylpentanoyl-CoA (valproyl-CoA) and its beta-oxidation metabolites facilitated a study of valproate metabolism in coupled rat liver mitochondria. Mitochondrial metabolites identified by high-performance liquid chromatography were 2-propylpentanoyl-CoA, 3-keto-2-propylpentanoyl-CoA, 2-propyl-2-pentenoyl- CoA, and trace amounts of 3-hydroxy-2-propylpentanoyl-CoA. It is concluded that valproic acid enters mitochondria where it is converted to 2-propylpentanoyl-CoA, dehydrogenated to 2-propyl-2-pentenoyl-CoA by 2-methyl-branched chain acyl-CoA dehydrogenase, and hydrated by enoyl-CoA hydratase to 3-hydroxy-2-propylpentanoyl-CoA.(ABSTRACT TRUNCATED AT 250 WORDS)
Li
J
J
Department of Chemistry, City College of the City University of New York, New York 10031.
Norwood
D L
DL
Mao
L F
LF
Schulz
H
H
D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D002451:Cell Compartmentation; D002851:Chromatography, High Pressure Liquid; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D013058:Mass Spectrometry; D008830:Microbodies / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D014635:Valproic Acid / Q000378:metabolism*
D000214:Acyl Coenzyme A; D005229:Fatty Acids, Monounsaturated; C045022:2-propyl-4-pentenoic acid; D014635:Valproic Acid