Probable disulfide isomerase, which participates in the folding of proteins containing disulfide bonds. May act as a dithiol oxidase (By similarity). Catalyzes the rearrangement of -S-S- bonds in proteins. The di-lysine motif confers endoplasmic reticulum localization for type I membrane proteins. N-glycosylated. Belongs to the protein disulfide isomerase family.