Cell type-specific expression of unique carbohydrate structures on cell surface glycoproteins and glycolipids provides information relevant to cell-cell interactions in developing and adult organisms. Sialyltransferases contribute to the diversity of carbohydrate structures through their attachment of sialic acid in various terminal positions on glycolipid and on glycoprotein (N-linked and O-linked) carbohydrate groups. The N-acetyllactosaminide alpha2,3 sialyltransferase (ST3GAL-III), also known as SIAT6 and ST3GAL3, is a type II membrane protein that catalyzes the transfer of sialic acid from CMP-sialic acid to galactose-containing substrates. Localized to the Golgi apparatus and the Golgi stack membrane, St3Gal-III is secreted into the body fluid. Twenty-six named isoforms of St3Gal-III exist as a result of alternative splicing events.
