Sialyltransferases Golgi

CMP, CDP, CTP, and synthetic derivatives of these nueleotides have been found to inhibit sialyltransferase activity.301" 02 Interest in such inhibitors is increasing, as they may be expected to serve as anticancer agents.269 901,303 Therefore, regulation of Golgi sialyltransferase activity appears possible by nucleotides as products of sialyl- and other glycosyl-transferase activities.1" 2 Interestingly, Epstein-Barr virus infection of human B, lymphoblastoid cell-lines leads to a diminution of sialyltransferase activity.304... 

Keenan, T. W. 1974B. Membranes of mammary gland. IX. Concentration of glyco-sphingolipid galactosyl and sialyltransferases in Golgi apparatus from bovine mammary gland. J. Dairy Sci. 57, 187-192. 

A continuous sucrose gradient of the total homogenate from young rat brain and electron microscopic examination of these fractions found most of the sialyltransferase activities to be localized in smooth microsomal membrane and Golgi complex derivatives and not associated with synaptosomes. 

Kitazume, S., Tachida, Y, Oka, R., Shirotani, K., Saido, T.C. and Hashimoto, Y, (2001) Alzheimer s P-secretase, P-site amyloid precursor protein-cleaving enzyme, is responsible for cleavage secretion of a Golgi-resident sialyltransferase. Proc. Natl Acad. Sci. U.S.A. 98, 13554. 

Melkerson-Watson LJ, Sweeley CC. Purification to apparent homogeneity by immunoaffinity chromatography and partial characterization of the GM3 gangUoside-forming enzyme, CMP-sialic acid lactosylceramide alpha 2,3-sialyltransferase (SAT-1), from rat liver Golgi. J. Biol. Chem. 1991 266 4448-4457. 

Chen TL, Chen C, Bergeron NQ, Qose BE, Bohrer TJ, Vertel BM, Colley KJ. The two rat a2,6-sialyltransferase (ST6Gal I) isoforms evaluation of catalytic activity and intra-Golgi localization. Glycobiology 2003 13(2) 109-117. 

Kono M, Takashima S, Liu H, Inoue M, Kojima N, Lee YC, Hamamoto T, Tsuji S. Molecular cloning and functional expression of a fifth-type alpha 2,3-sialyltransferase (mST3Gal V GM3 synthase). Biochem. Biophys. Res. Commun. 1998 253-175. Daniotti JL, Martina JA, Giraudo CG, Zurita AR, Maccioni HJ. GM3 alpha2,8-sialyltransferase (GD3 synthase) protein characterization and sub-golgi location in CHO-Kl cells. J. Neurochem. 2000 74 1711-1720. 

The sialyltransferases are membrane-bound proteins located in the endoplasmic reticulum (ER) and in the Golgi apparatus. Information about their sequence homology is limited, but they do appear to share a common topography [35]. A catalytic domain resides at the C-terminus followed by an N-terminal segment that anchors the enzyme into the ER or Golgi membrane. Soluble, catalytically active sialyltransferases that lack the anchor segment have been isolated from milk, serum, and other body fluids, suggesting that this N-terminal anchor is not necessary for the enzyme to retain catalytic activity. However, the ability to obtain from natural sources quantities of most sialyltransferases that would be needed for synthesis applications is hampered by low tissue concentrations and difficult purifications. 

In eukaryotes, sialyltransferases are located in the Golgi compartments [126,127]. They transfer a sialic acid residue from CMP-sialic acid to a noiueducing Gal-, GalNAc-, GlcNAc-, or sialic acid residue via an a-glycosidic linkage. The possible linkages include a2,3, a2,6, or a2,8, and each is the product of a different sialyltransferase. 

Asialoglycoprotein receptor Transferrin receptor Sucrase-isomaltase precursor Golgi galactosyltransferase Golgi sialyltransferase Influenza HN protein... 

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