FunctionIt may be responsible for the synthesis of the sequence NeuAc-alpha-2,3-Gal-beta-1,3-GalNAc- found on sugar chains O-linked to Thr or Ser and also as a terminal sequence on certain gangliosides. SIAT4A and SIAT4B sialylate the same acceptor substrates but exhibit different Km values.
Tissue specificityExpressed in several tissues. Highest expression in lung, liver, skeletal muscle, kidney, pancreas, spleen and placenta.
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.