FunctionIt may be responsible for the synthesis of the sequence NeuAc-alpha-2,3-Gal-beta-1,3-GalNAc- found in terminal carbohydrate groups of certain glycoproteins, oligosaccharides and glycolipids. SIAT4A and SIAT4B sialylate the same acceptor substrates but exhibit different Km values.
Tissue specificityHighly expressed in skeletal muscle and heart and to a much lesser extent in brain, placenta, liver and pancreas. Scarcely detectable in lung and kidney.
PathwayProtein modification; protein glycosylation.
Sequence similaritiesBelongs to the glycosyltransferase 29 family.
Post-translational modificationsThe soluble form derives from the membrane form by proteolytic processing.
Cellular localizationGolgi apparatus > Golgi stack membrane. Secreted. Membrane-bound form in trans cisternae of Golgi. Secreted into the body fluid.