Disulfide isomerase which catalyzes the formation, isomerization, and reduction or oxidation of disulfide bonds (By similarity). Associates with calcitriol, the active form of vitamin D3 which mediates the action of this vitamin on cells (By similarity). Association with calcitriol does not affect its enzymatic activity (By similarity). Catalyzes the rearrangement of -S-S- bonds in proteins. Interacts with ERP27 and CANX. Interacts with MZB1 in a calcium-dependent manner. Interacts with SERPINA2 and with the S and Z variants of SERPINA1. Interacts with ATP2A2. Predominantly expressed in liver. Low in brain, testis and colon. Not detectable in pancreas and skeletal muscle. Belongs to the protein disulfide isomerase family.