Catalyzes the oxidation of sulfhydryl groups in peptide and protein thiols to disulfides with the reduction of oxygen to hydrogen peroxide. Plays a role in disulfide bond formation in a variety of extracellular proteins. In fibroblasts, required for normal incorporation of laminin into the extracellular matrix, and thereby for normal cell-cell adhesion and cell migration. O2 + 2 R'C(R)SH = H2O2 + R'C(R)S-S(R)CR' Binds 1 FAD per subunit. Monomer. Detected in endometrium and in uterus glandular epithelial cells (at protein level). Expressed in testis, placenta, pancreas, lung, ovary, endometrium, but not in brain, liver and kidney tissues. Higher expression in epithelial cells. N-glycosylated. O-glycosylated on Thr and Ser residues. Belongs to the quiescin-sulfhydryl oxidase (QSOX) family.