alpha-Lipoic acid dependent regeneration of ascorbic acid from dehydroascorbic acid in rat liver mitochondria

J Bioenerg Biomembr. 1996 Feb;28(1):77-85.

Abstract

Rat liver mitochondria were examined for their ability to reduce dehydroascorbic acid to ascorbic acid in an alpha-lipoic acid dependent or independent manner. The alpha-lipoic acid dependent reduction was stimulated by factors that increased the NADH dependent reduction of alpha-lipoic acid to dihydrolipoic acid in coupled reactions. Optimal conditions for dehydroascorbic acid reduction to ascorbic acid were achieved in the presence of pyruvate, alpha-lipoic acid, and ATP. Electron transport inhibitors, rotenone and antimycin A, further enhanced the dehydroascorbic acid reduction. The reactions were strongly inhibited by 1 mM iodoacetamide or sodium arsenite. Mitoplasts were qualitatively similar to intact mitochondria in dehydroascorbate reduction activity. Pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase reduced dehydroascorbic acid to ascorbic acid in an alpha-lipoic acid, coenzyme A, and pyruvate or alpha-ketoglutarate dependent fashion. Dehydroascorbic acid was also catalytically reduced to ascorbic acid by purified lipoamide dehydrogenase in an alpha-lipoic acid (K0.5 = 1.4 +/- 0.8 mM) and lipoamide (K0.5 = 0.9 +/- 0.3 mM) dependent manner.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
  • Animals
  • Antimycin A / pharmacology
  • Ascorbic Acid / metabolism*
  • Dehydroascorbic Acid / metabolism*
  • Dihydrolipoamide Dehydrogenase / metabolism
  • In Vitro Techniques
  • Ketone Oxidoreductases / metabolism
  • Kinetics
  • Mitochondria, Liver / drug effects*
  • Mitochondria, Liver / metabolism*
  • Models, Biological
  • Multienzyme Complexes / metabolism
  • Oxidation-Reduction
  • Rats
  • Rats, Sprague-Dawley
  • Rotenone / pharmacology
  • Thioctic Acid / pharmacology*
  • Uncoupling Agents / pharmacology

Substances

  • Multienzyme Complexes
  • Uncoupling Agents
  • Rotenone
  • Antimycin A
  • Thioctic Acid
  • Ketone Oxidoreductases
  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
  • Dihydrolipoamide Dehydrogenase
  • Ascorbic Acid
  • Dehydroascorbic Acid