Polypeptide N-acetylgalactosaminyltransferase 3(GALNT3) belongs to the glycosyltransferase 2 family and galNAc-T subfamily. It expressed in organs that contain secretory epithelial glands and it highly expressed in pancreas, skin, kidney and testis. There are two conserved domains in the glycosyltransferase region: the N-terminal domain (domain A, also called GT1 motif), which is probably involved in manganese coordination and substrate binding and the C-terminal domain (domain B, also called Gal/GalNAc-T motif), which is probably involved in catalytic reaction and UDP-Gal binding .This protein plays a major role in regulating phosphate levels within the body (phosphate homeostasis). Among its many functions, phosphate plays a critical role in the formation and growth of bones in childhood and helps maintain bone strength in adults.