We observed that mice lacking the enzyme Quiescin Sulfhydryl Oxidase 1 (QSOX1) produce defective colon mucus and show impaired mucosal barrier function. However, an investigation on the molecular level revealed normal disulfide-mediated polymerization of mucins in the QSOX1 knockout mice. We found instead that sialic acid decoration of glycoproteins in colon tissue was perturbed, leading to the discovery that QSOX1 forms regulatory disulfides in Golgi sialyltransferases. The link between QSOX1, Golgi redox regulation, and sialic acid addition is of potential medical importance, as sialylation defects in the colon are known to cause colitis in humans.
