Mucin synthesis. UDP-GlcNAc:GalNAc-R beta 3-N-acetylglucosaminyltransferase and UDP-GlcNAc:GlcNAc beta 1-3GalNAc-R (GlcNAc to GalNAc) beta 6-N-acetylglucosaminyltransferase from pig and rat colon mucosa.
Pig and rat colon mucosal membrane preparations catalyze the in vitro transfer of N-acetyl-D-glucosamine (GlcNAc) from UDP-GlcNAc to GalNAc-ovine submaxillary mucin to form GlcNAc beta 1-3GalNAc-mucin. Rat colon also catalyzes the in vitro transfer of GlcNAc from UDP-GlcNAc to GlcNAc beta 1-3GalNAc-mucin to form GlcNAc beta 1-3(GlcNAc beta 1-6) GalNAc-mucin. This is the first demonstration of in vitro synthesis of the GlcNAc beta 1-3GalNAc disaccharide and of the GlcNAc beta 1-3-(GlcNAc beta 1-6)GalNAc trisaccharide, two of the four major core types found in mammalian glycoproteins of the mucin type, i.e., those containing oligosaccharides with GalNAc-alpha-serine (threonine) linkages. The activity catalyzing synthesis of the disaccharide has been named UDP-GlcNAc:GalNAc-R beta 3-N-acetylglucosaminyltransferase (mucin core 3 beta 3-GlcNAc-transferase), while the activity responsible for synthesizing the trisaccharide has been named UDP-GlcNAc:GlcNAc beta 1-3GalNAc-R (GlcNAc to GalNAc) beta 6-N-acetylglucosaminyltransferase (mucin core 4 beta 6-GlcNAc-transferase). The beta 3-GlcNAc-transferase from pig colon is activated by Triton X-100, has an absolute requirement for Mn2+, and transfers GlcNAc to GalNAc-alpha-phenyl, GalNAc-alpha-benzyl, and GalNAc-ovine submaxillary mucin with apparent Km values of 5, 2, and 3 mM and Vmax values of 59, 62, and 37 nmol h-1 (mg of protein)-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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D000818:Animals; D002240:Carbohydrate Sequence; D002250:Carbon Radioisotopes; D003106:Colon / Q000201:enzymology*; D005964:Glucosyltransferases / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000201:enzymology*; D007700:Kinetics; D009077:Mucins / Q000096:biosynthesis*; D017351:N-Acetylglucosaminyltransferases; D009844:Oligosaccharides / Q000138:chemical synthesis; D051381:Rats; D013045:Species Specificity; D013552:Swine; D014018:Tissue Distribution
D002250:Carbon Radioisotopes; D009077:Mucins; D009844:Oligosaccharides; D005964:Glucosyltransferases; D017351:N-Acetylglucosaminyltransferases; C046236:acetylgalactosaminyl-O-glycosyl-glycoprotein beta-1,3-N-acetylglucosaminyltransferase; C039548:UDP-N-acetylglucosamine-galactose(1-6)-N-acetylglucosaminyltransferase