Modulation of Glutathione S-Transferase Activity by a Thiol/Disulfide Exchange Reaction and Involvement of Thioltransferase

Cloning, High Level-expression and Characterization of Human Lens Thioltransferase

“…Another interesting observation is that unlike gamma crystallin-cystine mixed disulfide, alpha crystallincystine mixed disulfide could not be dethiolated by lens TTase suggesting that the lens TTase has the ability to dethiolate cystine mixed disulfides but has a preference for the proteins that have been conjugated to cystine. This is in agreement with the report of Terada et al (1993) who have shown that inactivated glutathione S transferase due to the formation of mixed disulfide with cystine could be easily dethiolated and reactivated by placental TTase. However, Gravina and Mieyal (1993) from their studies have reported that while TTase efficiently dethiolated PSSG, PSSC could not be dethiolated.…”

Does Glutathione-S-Transferase Dethiolate Lens Protein-Thiol Mixed Disulfides?—A Comparative Study With Thioltransferase

“…The lost activity, however, could be restored after dethiolation with TTase (Terada et al, 1993 ;Mieyal et al, 1995 ;Qiao et al, 1998), although the mechanism on how TTase dethiolates GST-SS-cysteamine is still a controversy (Mieyal et al, 1995). In contrast, TTase is extremely resistant to oxidative stress, as demonstrated in H # O # treated rabbit lens epithelial cells .…”

Role of Glutathione S-Transferases in Lens under Oxidative Stress

“…19) The first report of this activity was presented in a paper on bovine lens GSTM by Raghavachari, N. et al 26) TTase, a small enzyme of < 10 kDa, can catalyze the thiol/ disulfide exchange reaction between small molecular weight thiols and proteins, and plays an important role in the redox regulation of protein thiols in living cells. [27][28][29][30] We have previously reported that TTase displays a strong sensitivity against oxidants, including disulfides. However, GSTMs show a potent resistance to oxidants and prooxidants, including H 2 O 2 , organic peroxides and naphthoquinone.…”

“…This TTase-like activity is apparently generated despite the fact that GSTM doesn't have the TTase motif (Cys-x-x-Cys) which is widely conserved in the characterisitic enzymes having a thiol/ disulfide exchange reaction such as TTase (glutaredoxin, Grx), thioredoxin (Trx) and protein disulfide isomerase (PDI). 29) GSTM1-1 may be involved in the p38 signaling pathway to protect cells from apoptosis through a dissociation from apoptosis signal-regulating kinase 1 (Ask1) in the presence of heat shock proteins under oxidative stress. 31) This result has made it evident that overexpression of GSTM1-1 inhibits the induction of p38 in the cells.…”

“…29,[32][33][34][35][36][37][38] A typical GSTP which exists in human placenta shows an efficient inactivation under oxidative conditions (oxidative stress) induced with oxidants (disulfides, H 2 O 2 , superoxide anion) and a prooxidant (naphthoquinone). However, the resulting inactivated GSTP is effectively restored to its activity by treatment with thiols including GSH, cysteamine and dithiothreitol, but not other chemical reductants such as butylated hydroxytoluene, α-tocopherol, ascorbate, uric acid, mannitol, tyrosine, tryptophan, histidine, quercitrin or bilirubin.…”