Acts as a protein-folding catalyst that interacts with nascent polypeptides to catalyze the formation, isomerization, and reduction or oxidation of disulfide bonds. Catalyzes the rearrangement of -S-S- bonds in proteins. Interacts with MEE8 and MED37A. A number of isoforms are produced. According to EST sequences. Expressed in germinating seedling, including the cotyledons and hypocotyl, in vascular tissues, in pollen grains, root tips, leaf trichomes, developing seeds and siliques. No visible phenotype, probably due to functional redundancy. Belongs to the protein disulfide isomerase family.