Effect Of Glutathione On The Phospholipase A2 Activity Of Peroxiredoxin 6

Peroxiredoxin 6 (Prdx6) is a unique non‐seleno 1‐Cys peroxidase with both peroxidase and phospholipase A 2 (PLA 2 ) activities. We have shown that phosphorylation of Prdx6 at Thr177 increases its PLA 2 activity and broadens its pH‐activity spectrum (Biochem. J. 419:669, 2009). Our recent study indicates that a change in the conformation of Prdx6 upon its phosphorylation is the basis for enhanced enzymatic activity at pH 7.4 (Biochemistry. 51:5521–30. 2012). Here, we studied the effect of glutathione (GSH) on the PLA 2 activity of Prdx6 using biochemical and biophysical approaches. With 3 H‐DPPC as substrate, basal Prdx6 PLA 2 activity was 0.17 ± 0.1 nmole/min/mg and increased to 49 ± 1 nmole/min/mg upon addition of 5 mM GSH. Addition of other thiols (GSSG, DTT) had no effect. The enhancing effect of GSH on the PLA 2 activity of Prdx6 depended on the redox status of substrates and phosphorylation status of the enzyme. GSH has no effect on PLA 2 activity if the substrate is oxidized by Cu(2+)‐ ascorbate or if the enzyme is phosphorylated. By isothermal titration calorimetry (ITC), GSH interacts with Prdx6. Circular dichroism (CD) indicates that GSH induces a change of Prdx6 conformation. Thus, a change in the conformation of Prdx6 in the presence of GSH is the basis for enhancing effect of GSH on PLA 2 activity of non‐phosphorylated Prdx6 in the presence of reduced substrate. This work was supported by NIH grants HL102016 and HL19737