The protein encoded by this gene is a type II membrane protein that catalyzes the transfer of sialic acid from CMP-sialic acid to galactose-containing substrates. The encoded protein is normally found in the Golgi but can be proteolytically processed to a soluble form. This protein, which is a member of glycosyltransferase family 29, can use the same acceptor substrates as does sialyltransferase 4A. [provided by RefSeq, Jul 2008].