Reactivity of glutaredoxins 1, 2 and 3 fromEscherichia coliand protein disulfide isomerase towards glutathionyl-mixed disulfides in ribonuclease A

Abstract

We have examined the activity of protein disulfide isomerase (PDI) and glutaredoxin (Grx) 1, 2 and 3 from Escherichia coli to catalyze the cleavage of glutathionylated ribonuclease A (RNase‐SG) by 1 mM GSH to yield reduced RNase. Apparent K _m values for RNase‐SG were similar, 2–10 μM, for Grx 1, 3 and PDI but Grx 1 and Grx 3 showed 500‐fold higher turnover numbers than PDI. The atypical Grx 2 also catalyzed deglutathionylation by GSH, but had higher K _m and apparent turnover number values compared to the two classical Grx. Refolding of RNase in a glutathione redox buffer was catalyzed by PDI. However, it could be measured only after a characteristic lag phase that was shortened by all three E. coli Grxs in a concentration‐dependent manner. A role of the glutaredoxin mechanism in the endoplasmic reticulum is suggested.