PDI is specifically responsible for folding proteins in the ER.
In an unfolded protein, a cysteine residue forms a mixed disulfide with a cysteine residue in an active site (CGHC motif) of protein disulfide-isomerase.
A second cysteine residue then forms a stable disulfide bridge within the substrate, leaving protein disulfide-isomerase's two active-site cysteine residues in a reduced state.

Afterwards, PDI can be regenerated to its oxidized form in the endoplasmic reticulum by transferring electrons to reoxidizing proteins such ER oxidoreductin 1 (Ero 1), VKOR (vitamin K epoxide reductase), glutathione peroxidase (Gpx7/8), and PrxIV (peroxiredoxin IV).
Ero1 is thought to be the main reoxidizing protein of PDI, and the pathway of reoxidation of PDI for Ero1 is more understood than that of other proteins.
Ero1 accepts electrons from PDI and donates these electrons to oxygen molecules in the ER, which leads to the formation of hydrogen peroxide.
PDI is specifically responsible for folding proteins in the ER. In an unfolded protein, a cysteine residue forms a mixed disulfide with a cysteine residue in an active site (CGHC motif) of protein disulfide-isomerase. A second cysteine residue then forms a stable disulfide bridge within the substrate, leaving protein disulfide-isomerase's two active-site cysteine residues in a reduced state.
Afterwards, PDI can be regenerated to its oxidized form in the endoplasmic reticulum by transferring electrons to reoxidizing proteins such ER oxidoreductin 1 (Ero 1), VKOR (vitamin K epoxide reductase), glutathione peroxidase (Gpx7/8), and PrxIV (peroxiredoxin IV). Ero1 is thought to be the main reoxidizing protein of PDI, and the pathway of reoxidation of PDI for Ero1 is more understood than that of other proteins. Ero1 accepts electrons from PDI and donates these electrons to oxygen molecules in the ER, which leads to the formation of hydrogen peroxide.
Protein disulfide-isomerase