RT Journal Article
SR Electronic
T1 VALPROYL-DEPHOSPHOCoA: A NOVEL METABOLITE OF VALPROATE FORMED IN VITRO IN RAT LIVER MITOCHONDRIA
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1304
OP 1310
DO 10.1124/dmd.32.11.1304
VO 32
IS 11
A1 Silva, Margarida F. B.
A1 IJlst, Lodewijk
A1 Allers, Paul
A1 Jakobs, Cornelis
A1 Duran, Marinus
A1 de Almeida, Isabel Tavares
A1 Wanders, Ronald J. A.
YR 2004
UL http://dmd.aspetjournals.org/content/32/11/1304.abstract
AB The mitochondrial metabolism of valproic acid (VPA) was investigated in vitro to elucidate its β-oxidation pathway since the characterization of VPA intermediates in the acyl-CoA thioester form, and not just in their free acid form, has not been fully achieved. Intact rat liver mitochondria were incubated with [4,5-3H2]VPA and [2-3H]VPA. The respective intermediates, valproyl-CoA, Δ2(E)-valproyl-CoA, 3-hydroxyvalproyl-CoA, and 3-oxovalproyl-CoA were analyzed by reverse phase high performance liquid chromatography (HPLC) with radioisotope and UV detection. An unknown metabolite, originating from both labeled substrates, was detected. It was identified as valproyl-dephosphoCoA (valproyl-dephCoA) by fast atom bombardment mass spectrometry (FAB-MS) analysis of the corresponding HPLC peak fraction. The FAB-MS spectrum of the authentic chemically synthesized valproyl-dephCoA proved to be consistent with that of the unknown compound. Valproyl-dephCoA is produced from valproyl-CoA in mitochondria, probably via a phosphatase-catalyzed reaction. This conversion was shown to be more dependent on the energy state involving [AXP] ([AXP] = [ATP] + [ADP] + [AMP]) and [phosphate] concentrations rather than the strict mitochondrial [ATP]/[ADP] ratio. The results indicate that higher concentrations of AXP and phosphate inhibit the dephosphorylation of valproyl-CoA. A complete understanding of the toxic significance of valproyl-dephCoA formation in vivo as a potential inhibitor of fatty acid β-oxidation is important to clarify the pathogenesis of VPA-associated hepatotoxicity. The American Society for Pharmacology and Experimental Therapeutics