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Homocysteine effects on cellular glutathione peroxidase (GPx-1) activity under in vitro conditions

Ayşen Durmaz1, Nurten Dikmen

  • 1Department of Biochemistry, Faculty of Medicine, Cukurova University, Adana, Turkey. aysendurmaz@yahoo.com

Journal of Enzyme Inhibition and Medicinal Chemistry
|February 2, 2008
PubMed

Insights

Severe hyperhomocysteinemia inhibits glutathione peroxidase (GPx) activity, particularly at low glutathione levels. However, cysteine can increase GPx activity under similar conditions.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Medical Science

Background:

  • Hyperhomocysteinemia is linked to various diseases, including cardiovascular conditions and neural tube defects.
  • The precise mechanisms underlying these disease associations remain unclear.
  • Homocysteine and cysteine are thiol-containing amino acids with potential biological roles.

Purpose of the Study:

  • To investigate the impact of homocysteine (Hcy) and cysteine (Cys) on glutathione peroxidase (GPx) activity.
  • To elucidate the role of these amino acids in oxidative stress pathways.

Main Methods:

  • Enzyme activity assays were performed to measure GPx-1 activity.
  • Experiments were conducted under varying concentrations of Hcy, Cys, and glutathione (GSH).

Main Results:

  • GPx-1 activity was significantly inhibited under conditions of severe hyperhomocysteinemia (50-500 microM Hcy).
  • This inhibition was more pronounced at low glutathione concentrations.
  • Cysteine demonstrated a contrasting effect, increasing GPx-1 activity at low glutathione levels.
  • Enzyme inhibition was observed at a high cysteine concentration (500 microM Cys).

Conclusions:

  • Hyperhomocysteinemia may impair antioxidant defense mechanisms by inhibiting GPx activity.
  • Cysteine's effect on GPx activity is concentration-dependent and differs from homocysteine.
  • These findings contribute to understanding the biochemical basis of diseases associated with altered homocysteine metabolism.

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