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

Hyperhomocysteinemia is associated with a lot of diseases including cardiovascular diseases and neural tube defect, but it has not been clarified exactly which mechanism is responsible for occurence disease. Here, homocysteine (Hcy) and cysteine (Cys), which are thiol containing amino acids, were examined for their effect on glutathione peroxidase (GPx) activity. It was observed that the GPx-1 activity was inhibited under severe hyperhomocysteinemia (50-500 mu M Hcy) conditions, especially at low glutathione concentrations but that cysteine increased GPx-1 activity at low glutathione concentrations and inhibition clearly appeared at 500mM Cys concentration.