title: Characterization of a sialyl alpha 2-3 transferase and a sialyl alpha 2-6 transferase from human platelets occurring in the sialylation of the N-glycosylproteins.
abstract: Two sialyltransferases (EC 2.4.99.-) are extracted with Triton X-100 from human platelets and characterized with asialo 3H-labelled alpha 1-acid glycoprotein, an N-glycosylprotein. Methylation analysis of their specificities indicates that the enzymes transfer selectively sialic acid in a 3 or 6 position to oligosaccharides possessing Gal(beta 1-4)GlcNAc structure. The sialyl alpha 2-3 transferase was separated from the sialyl alpha 2-6 transferase by Ultrogel AcA34 column chromatography. Through affinity chromatography on CDPethanolamine-Sepharose, the two sialyltransferases are partly purified (5- and 20-fold enrichment of their specific activity, respectively, for sialyl alpha 2-3 transferase and alpha 2-6 transferase) and appear to be structurally heterogeneous.
mesh_terms: D001792:Blood Platelets / Q000201:enzymology*; D006801:Humans; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000097:blood; D012799:Sialyltransferases / Q000097:blood* / Q000302:isolation & purification; D013379:Substrate Specificity; D014166:Transferases / Q000097:blood*
chemical_list: D012795:Sialoglycoproteins; D014166:Transferases; D012799:Sialyltransferases