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Protein disulfide isomerase and glutathione are alternative substrates in the one Cys catalytic cycle of glutathione peroxidase 7.
Biochim. Biophys. Acta-Gen. Subj. 1830, 3846-3857 (2013)
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=5.2μM 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.
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Publikationstyp
Artikel: Journalartikel
Dokumenttyp
Wissenschaftlicher Artikel
Schlagwörter
Kinetics; Glutathione peroxidase; Peroxide; Redox switch; Redoxin; OXIDATIVE STRESS; THIOREDOXIN; MECHANISM; SELENOCYSTEINE; SPECIFICITY; PHGPX; STATE; GENE; CELL; GPX
ISSN (print) / ISBN
0304-4165
e-ISSN
1872-8006
Zeitschrift
Biochimica et Biophysica Acta - General Subjects
Quellenangaben
Band: 1830,
Heft: 6,
Seiten: 3846-3857
Verlag
Elsevier
Nichtpatentliteratur
Publikationen
Begutachtungsstatus
Peer reviewed
Institut(e)
Institute of Developmental Genetics (IDG)