Methylselenol Formed by Spontaneous Methylation of Selenide Is a Superior Selenium Substrate to the Thioredoxin and Glutaredoxin Systems
Figure 3
A–D. Oxidation of NADPH by the thioredoxin and glutaredoxin systems in the presence of selenite and GS-Se-SG, catalyzed by SAM.
Reaction catalyzed by the thioredoxin system was performed in 50 mM Tris-HCl, 1 mM EDTA, pH 7.5, and 200 µM NADPH. A) The reaction mixture contained 2 µM human Trx1 and 50 nM mammalian TrxR1. SAM, 4 mM (♦) Selenite (5 µM) (○), SAM and selenite, 4 mM and 5 µM respectively (without Trx1 in the reaction) (•), SAM and selenite (Δ). B) Reaction catalyzed by the glutaredoxin system was performed in TE-buffer, containing 200 µM NADPH, 6 µg/mL GR, 1 µM human Grx1 and 50 µM GSH. SAM, 4 mM (♦) Selenite (5 µM) (○), SAM and selenite, 4 mM and 5 µM respectively (without Grx1 in the reaction) (•), SAM and selenite, 4 mM and 5 µM respectively (Δ). C) The thioredoxin system with: 5 µM GS-Se-SG (without Trx1 in the reaction) (♦), 5 µM GS-Se-SG (•), 5 µM GS-Se-SG and SAM (without Trx1 in the reaction) (○), 5 µM GS-Se-SG and SAM (Δ). D) The glutaredoxin system with: 15 µM GS-Se-SG (♦), GS-Se-SG and SAM (•), GS-Se-SG and 1 µM Grx1 (○), GS-Se-SG, SAM and 1 µM Grx1 (Δ).