GALNT3 : polypeptide N-acetylgalactosaminyltransferase 3
Description
The GALNT3 (polypeptide N-acetylgalactosaminyltransferase 3) is a protein-coding gene located on chromosome 2.
The GALNT3 gene provides instructions for making the ppGalNacT3 protein, found in many cell types. This protein is crucial for regulating phosphate levels (phosphate homeostasis). Phosphate plays a vital role in bone formation and growth during childhood and helps maintain bone strength in adults. The kidneys regulate phosphate levels by excreting excess phosphate in urine and reabsorbing it into the bloodstream when needed. The ppGalNacT3 protein controls the activity of fibroblast growth factor 23 (FGF23), produced by bone cells. FGF23 signals the body to reduce phosphate reabsorption by the kidneys. ppGalNacT3 attaches sugar molecules to FGF23 through a process called glycosylation. These sugar molecules are essential for FGF23's transport out of cells and protection from breakdown. When phosphate levels are high, ppGalNacT3 glycosylates FGF23, preventing its breakdown. Signaling from FGF23 then decreases phosphate reabsorption, helping maintain normal phosphate levels.
GALNT3 catalyzes the initial step in O-linked oligosaccharide biosynthesis, transferring an N-acetyl-D-galactosamine residue to serine or threonine residues on protein receptors. It has been shown to glycosylate various proteins, including HIV envelope glycoprotein gp120, EA2, MUC2, MUC1A, MUC5AC, and likely fibronectin in vivo. It also glycosylates FGF23, which plays a crucial role in phosphate homeostasis.
GALNT3 is also known as GalNAc-T3, HFTC, HFTC1, HHS.
