Inactivation of beef brain α-ketoglutarate dehydrogenase complex by valproic acid and valproic acid metabolites: Possible mechanism of anticonvulsant and toxic actions

Anthony S. Luder, Janice K. Parks, F. Frerman, William Davis Parker

Research output: Contribution to journalArticlepeer-review

53 Scopus citations

Abstract

The anticonvulsant valproic acid (VPA, 2-n-propylpentanoic acid) causes inhibition of the citric acid cycle and elevations of central nervous system (CNS) γ-aminobutyric acid (GABA) levels, which correlates with anticonvulsant action. No unifying mechanism for these actions of VPA has won general acceptance. α-Ketoglutarate dehydrogenase complex (KDHC) is a critical control enzyme in the CNS. We hypothesized that VPA may be an inhibitor of this enzyme since decreased KDHC activity would reduce substrate flux through the citric acid cycle and may increase flux into GABA synthesis. To test this hypothesis, inhibition of purified beef brain KDHC by VPA and its metabolites 2-n-propylpent-2-enoic acid (Δ2,3 VPE) and their coenzyme A (CoA) derivatives were studied. Preincubation of the NADH-reduced enzyme with Δ2,3 VPE, VPA-CoA, and Δ2,3 VPE-CoA caused time-dependent inactivation, reversible by addition of CoA. Under steady-state conditions, Δ2,3 VPE and VPA-CoA were competitive inhibitors of KDHC and Δ2,3 VPE-CoA was a mixed inhibitor. These observations have implications for the molecular mechanisms of VPA action. VPA derivatives cause inactivation and inhibition of KDHC, which may explain the anticonvulsant and some toxic actions of VPA.

Original languageEnglish
Pages (from-to)1574-1581
Number of pages8
JournalJournal of Clinical Investigation
Volume86
Issue number5
StatePublished - Nov 1990
Externally publishedYes

Keywords

  • Alpha-ketoglutarate dehydrogenase complex
  • Anti-convulsant
  • Gamma-aminobutyric acid
  • Reye syndrome
  • Valproic acid

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