This entry represents a group disulfide-isomerases, including PDIA6 from animals, Mpd1 from yeasts and PDI22/PDI23 from Arabidopsis. Protein-disulfide isomerase (PDI) is a resident of the endoplasmic reticulum (ER) that catalyses the formation, reduction, and isomerization of disulfide bonds. PDIA6 is an active oxidoreductase with similar enzymatic properties to other PDIs; however, it doesn't seem to be involved directly in protein folding. Instead, it regulates the unfolded protein response (UPR) through controlling the decay of IRE1alpha signaling via disulfide-dependent association []. Mpd1 have oxidative refolding activity and interacts with Cne1, an integral membrane ER chaperone involved in folding and quality control of glycoproteins [].