| First Author | Bosello-Travain V | Year | 2013 |
| Journal | Biochim Biophys Acta | Volume | 1830 |
| Issue | 6 | Pages | 3846-57 |
| PubMed ID | 23454490 | Mgi Jnum | J:202430 |
| Mgi Id | MGI:5519015 | Doi | 10.1016/j.bbagen.2013.02.017 |
| Citation | Bosello-Travain V, et al. (2013) Protein disulfide isomerase and glutathione are alternative substrates in the one Cys catalytic cycle of glutathione peroxidase 7. Biochim Biophys Acta 1830(6):3846-57 |
| abstractText | BACKGROUND: Mammalian GPx7 is a monomeric glutathione peroxidase of the endoplasmic reticulum (ER), containing a Cys redox center (CysGPx). Although containing a peroxidatic Cys (CP) it lacks the resolving Cys (CR), that confers fast reactivity with thioredoxin (Trx) or related proteins to most other CysGPxs. METHODS: Reducing substrate specificity and mechanism were addressed by steady-state kinetic analysis of wild type or mutated mouse GPx7. The enzymes were heterologously expressed as a synuclein fusion to overcome limited expression. Phospholipid hydroperoxide was the oxidizing substrate. Enzyme-substrate and protein-protein interaction were analyzed by molecular docking and surface plasmon resonance analysis. RESULTS: Oxidation of the CP is fast (k+1>10(3)M(-1)s(-1)), however the rate of reduction by GSH is slow (k'+2=12.6M(-1)s(-1)) even though molecular docking indicates a strong GSH-GPx7 interaction. Instead, the oxidized CP can be reduced at a fast rate by human protein disulfide isomerase (HsPDI) (k+1>10(3)M(-1)s(-1)), but not by Trx. By surface plasmon resonance analysis, a KD=5.2muM was calculated for PDI-GPx7 complex. Participation of an alternative non-canonical CR in the peroxidatic reaction was ruled out. Specific activity measurements in the presence of physiological reducing substrate concentration, suggest substrate competition in vivo. CONCLUSIONS: GPx7 is an unusual CysGPx catalyzing the peroxidatic cycle by a one Cys mechanism in which GSH and PDI are alternative substrates. GENERAL SIGNIFICANCE: In the ER, the emerging physiological role of GPx7 is oxidation of PDI, modulated by the amount of GSH. |
