Solubilized glycosyltransferases and biosynthesis in vitro of glycolipids.
The assembly of most of the ceramide-linked glycolipids (GSLs) in eukaryotic cells occurs in Golgi bodies. At least 18 different glycolipid:glycosyltransferases (GSL:GLTs) have been characterized, 10 of which have been solubilized. These GLTs can be classified into 2 distinct groups: 1) GLTs dedicated to either Dol-P-P-sugar(s) or ceramide-linked sugar(s); and 2) GLTs with dual loyalties (i.e., they compete with glycolipid- and glycoprotein-bound oligosaccharides). Studies with solubilized and purified GalNAcT-1 and GalNAcT-2 from embryonic chicken brains prove that GalNAcT-1 (UDP-GalNAc:GM3 beta 1-4GalNAcT) is specific for GSL, whereas GalNAcT-2 (UDP-GalNAc:Gb3 beta 1-3GalNAcT) can transfer to an oligosaccharide containing the alpha-linked terminal galactose. Similarly, GalT-3 (UDP-Gal:GM2 beta 1-3GalT) is more specific for ganglio-oligosaccharide and GalT-4 (UDP-Gal:Lc3 beta 1-4GalT) can transfer galactose to N-acetylglucosamine linked to p-nitrophenol, glycolipid or glycoprotein. Both GalT-3 and GalT-4 have been separated and purified from embryonic chicken brains. Studies with solubilized SAT-4 and SAT-3, from bovine spleen and embryonic chicken brains, respectively, suggest the existence of 2 different gene-expressed alpha 2-3SATs. The newly discovered FucT-3 (GDP-Fuc:NeuGc-iLc6-alpha 1-3FucT) from human colon carcinoma (Colo-205) has also been solubilized and separated from other GSL:GLTs. Using a new activity gel-Western blot combined technique, the molecular mass of this FucT-3 was determined to be 105 kDa.
Basu
S
S
Department of Chemistry, University of Notre Dame, IN 46556.
Basu
M
M
Das
K K
KK
Daussin
F
F
Schaeper
R J
RJ
Banerjee
P
P
Khan
F A
FA
Suzuki
I
I
D000818:Animals; D002240:Carbohydrate Sequence; D005700:Galactosyltransferases / Q000378:metabolism; D006017:Glycolipids / Q000096:biosynthesis*; D006602:Hexosyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D015394:Molecular Structure; D017350:N-Acetylgalactosaminyltransferases; D012799:Sialyltransferases / Q000378:metabolism; D012995:Solubility
D006017:Glycolipids; D005700:Galactosyltransferases; D006602:Hexosyltransferases; D017350:N-Acetylgalactosaminyltransferases; C003742:UDPgalactosamine-galactose acetylgalactosaminyltransferase; D012799:Sialyltransferases