The possible physiological function of thioltransferase in cells.

We sought to study the possible physiological function of thioltransferase (TTase) in combating oxidative damage in the lens epithelial cells. The cells transfected with either TTase-containing plasmid or vector only were compared for their resistance to oxidative stress in the presence of a bolus of H2O2 (0.1 mM) for 3 h. Cells depleted of TTase activity upon cadmium treatment were also examined for the resistance to oxidative stress under the same conditions. TTase activity assay, Western blot, and Northern blot analyses confirmed that hTTase gene was successfully transfected into the HLE B3 cells and was overexpressed. The TTase-transfected cells detoxified H2O2 as efficiently as the control cells but displayed a faster and more complete recovery of oxidatively inactivated glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and glutathione peroxidase (GPx) activities and suppressed protein thiolation (PSSG formation). With TTase activity being inhibited by cadmium, the spontaneous reactivation of GAPDH under bolus H2O2 treatment was not accomplished in cadmium-pretreated cells. These data indicate a new physiological function of TTase, which involves in the reactivation of the oxidatively inactivated enzymes through dethiolation; thus this redox-regulating enzyme can protect the human lens epithelial cells and maybe other cell types by preventing them from permanent oxidative damage.