Molecular and Cellular Biochemistry

, Volume 209, Issue 1–2, pp 145–153

Dehydroascorbic acid irreversibly inhibits hexokinase activity

  • Mara Fiorani
  • Roberta De Sanctis
  • Francesca Scarlatti
  • Luciana Vallorani
  • Roberta De Bellis
  • Giordano Serafini
  • Marzia Bianchi
  • Vilberto Stocchi
Article

DOI: 10.1023/A:1007168032289

Cite this article as:
Fiorani, M., De Sanctis, R., Scarlatti, F. et al. Mol Cell Biochem (2000) 209: 145. doi:10.1023/A:1007168032289

Abstract

The oxidized form of vitamin C (dehydroascorbic acid, DHA) completely and irreversibly inactivates recombinant human hexokinase type I, in a pseudo-first order fashion. The inactivation reaction occurs without saturation, indicating that DHA does not form a reversible complex with hexokinase. Further characterization of this response revealed that the inactivation does not require oxygen and that dithiothreitol, while able to prevent the DHA-mediated loss of enzyme activity, failed to restore the activity of the DHA-inhibited enzyme. Inactivation was not associated with cleavage of the peptide chain or cross-linking. The decay in enzymatic activity was however both dependent on deprotonation of a residue with an alkaline pKa and associated with covalent binding of DHA to the protein. In addition, inactivation of hexokinase decreased or increased, respectively, in the presence of the substrates glucose or MgATP. Finally, amino acid analysis of the DHA-modified hexokinase revealed a decrease of cysteine residues.

Taken together, the above results are consistent with the possibility that covalent binding of the reagent with a thiol group of cysteine is a critical event for the DHA-mediated loss of hexokinase activity.

hexokinase dehydroascorbic acid thiol groups protein modification 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Mara Fiorani
    • 1
  • Roberta De Sanctis
    • 1
  • Francesca Scarlatti
    • 1
  • Luciana Vallorani
    • 1
  • Roberta De Bellis
    • 1
  • Giordano Serafini
    • 1
  • Marzia Bianchi
    • 1
  • Vilberto Stocchi
    • 1
  1. 1.Istituto di Chimica Biologica 'Giorgio Fornaini'Urbino (PU)Italy

Personalised recommendations