Fibroblast growth factor 23 (FGF23, aka phosphatonin) is a regulator of phosphate homeostasis and vitamin D metabolism. Its effects are thought to be mediated via the FGFR3c receptor. Glycosylation is necessary for FGF23 secretion from the cell and that is mediated by polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3), which transfers an N-acetylgalactosaminyl (GalNAc) moiety from a high energy donor to threonine 178 on FGF23 (Kato et al. 2006). Competition between proprotein convertase cleavage and O-glycosylation determines the level of secreted active FGF23.
Mandel, U, Jeanneau, C, Kato, K, Bennett, EP, Benet-Pages, A, Tarp, MA, Lorenz-Depiereux, B, Clausen, H, Strom, TM
polypeptide N-acetylgalactosaminyltransferase activity of GALNT3 [Golgi membrane]
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