Endoplasmic reticulum disulfide reductase involved both in the correct folding of proteins and degradation of misfolded proteins. Required for efficient folding of proteins in the endoplasmic reticulum by catalyzing the removal of non-native disulfide bonds formed during the folding of proteins, such as LDLR. Also involved in endoplasmic reticulum-associated degradation (ERAD) by reducing incorrect disulfide bonds in misfolded glycoproteins recognized by EDEM1. Interaction with HSPA5 is required its activity, not for the disulfide reductase activity, but to facilitate the release of DNAJC10 from its substrate. Promotes apoptotic signaling pathway in response to endoplasmic reticulum stress. Interacts with HSPA5 (via its J domain). Interacts with EDEM1. Ubiquitous. Particularly abundant in secretory tissues. Ubiquitous in fetal tissues and tumor tissues. Higher expression in fetal tissues than in adult tissues. Expressed in testis, pancreas, fetal thymus and fetal kidney. High expression in heart, liver, kidney, and testis. Low expression in spleen and skeletal muscle. Thioredoxin domains 3 and 4 are the primary reductase domains. The thioredoxin-like regions Trxb 1 and 2 lack a redox-active CXXC motif. Mice are viable and healthy but show enhanced endoplasmic reticulum stress response in the salivary gland.