Quiescin sulfhydryl oxidase 1 is an enzyme that in humans is encoded by the QSOX1gene.[5][6][7]
This gene encodes an enzyme that is localized primarily to the Golgi apparatus and secreted fluids.[8] QSOX1 is a multi-domain disulfide catalyst. Unlike other disulfide catalysts, QSOX1 can both generate disulfides de novo and catalyze dithiol/disulfide exchange. The de novo disulfide bond formation is catalyzed by the ERV1 domain that contains a FAD co-factor that allows depositions of electrons onto the terminal electron acceptor, typically molecular oxygen. The dithiol/disulfide exchange is catalyzed by the thioredoxin domain. The two domains are linked together by a flexible linker that allows the thioredoxin domain to first interact with the substrate protein and then regenerate by ERV1 domain.[9]
QSOX1 gene expression is induced as fibroblasts begin to exit the proliferative cycle and enter quiescence,[10][11] suggesting that this gene plays an important role in growth regulation. In fibroblasts QSOX1 is required for normal incorporation of laminin into the extracellular matrix, and thereby for normal cell-cell adhesion and cell migration.[12]
Two transcript variants encoding two different isoforms have been found for this gene.[13][7] The two isoforms have different tissue distribution and in addition isoform 1 has a transmembrane helix in the carboxy terminal while isoform 2 is a secreted soluble protein.
^Ilani T, Alon A, Grossman I, Horowitz B, Kartvelishvily E, Cohen SR, et al. (July 2013). "A secreted disulfide catalyst controls extracellular matrix composition and function". Science. 341 (6141): 74–76. Bibcode:2013Sci...341...74I. doi:10.1126/science.1238279. PMID23704371.
^* Radom J, Colin D, Thiebault F, Dognin-Bergeret M, Mairet-Coello G, Esnard-Feve A, et al. (May 2006). "Identification and expression of a new splicing variant of FAD-sulfhydryl oxidase in adult rat brain". Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression. 1759 (5): 225–233. doi:10.1016/j.bbaexp.200604008. PMID16806532.
Thorpe C, Hoober KL, Raje S, Glynn NM, Burnside J, Turi GK, et al. (September 2002). "Sulfhydryl oxidases: emerging catalysts of protein disulfide bond formation in eukaryotes". Archives of Biochemistry and Biophysics. 405 (1): 1–12. doi:10.1016/S0003-9861(02)00337-5. PMID12176051.
Coppock D, Kopman C, Gudas J, Cina-Poppe DA (March 2000). "Regulation of the quiescence-induced genes: quiescin Q6, decorin, and ribosomal protein S29". Biochemical and Biophysical Research Communications. 269 (2): 604–610. doi:10.1006/bbrc.2000.2324. PMID10708601.
