QSOX1 belongs to the family of FAD-dependent sulfhydryl oxidases and is an atypical disulfide catalyst. QSOX1 is mainly located in the Golgi apparatus and endoplasmic reticulum (ER) in human embryonic fibroblasts, and it cooperates with protein disulfide isomerase (PDI) to help fold new-born proteins in the cell. QSOX1 is mainly expressed in the heart, placenta, lung, liver, skeletal muscle, and pancreas, and is very weakly expressed in the brain and kidneys. Studies have found that the increase of QSOX1 expression in tumor cells enables tumor cells to actively circumvent the mechanism of apoptosis mediated by reactive oxygen species.
