Polysialic acid Polysialylated NCAM Polysialylation of NCAM1 Authored: Garapati, P V, 2009-05-30 17:44:08 EC Number: 2.4.99.8 Edited: Garapati, P V, 2009-05-30 17:44:08 NCAM in the developing brain is highly polysialylated and is referred as the embryonic form of NCAM. Polysialic acid is a developmentally regulated, anti-adhesive glycan with a linear homopolymer of alpha2,8-linked sialic acid units. They are mainly attached to the fifth and sixth N-glycosylation sites of the fifth Ig-like domain of NCAM. Polysialylation of NCAM is catalyzed by two polysialyltransferases, ST8Sia II (STX) and ST8Sia IV (PST), which belong to the family of six genes encoding alpha2,8-sialyltransferases. These enzymes add polysialic acid to NCAM N-glycans until it reaches a certain size (up to 200 sialic acid residues), where neither enzyme can interact with polysialylated N-glycans, and the polymerization of sialic acid is terminated.<br>Due to the structure with its chemical nature, polysialic acid can attenuate the interaction of NCAM with NCAM and other molecules in the same membrane (cis-interaction) or in another cell membrane (trans-interaction). During axonal growth the presence of polysialic acid along axons seems to prevent inappropriate synapse formation. Pubmed12765789 Pubmed16267048 Pubmed18059411 Reactome Database ID Release 43422454 Reactome, http://www.reactome.org ReactomeREACT_18324 Reviewed: Maness, PF, Walmod, PS, 2009--0-5- has a Stoichiometric coefficient of 2