Biosynthesis of blood group I and i antigens in rat tissues. Identification of a novel beta 1-6-N-acetylglucosaminyltransferase.
The beta-galactoside beta 1-6- and beta 1-3-N-acetylglucosaminyltransferases (beta 1-6GnT and beta 1-3GnT) that synthesize blood group I and i antigens were identified in rat tissues, using pyridylaminated lacto-N-neotetraose (Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-PA) as an acceptor. The products of the transferase reactions were separated on high performance liquid chromatography. The products of the transferase reactions were identified by 1H NMR as (formula; see text) and GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-PA. The product for beta 1-6GnT was also identified by methylation analysis. Kinetic experiments were carried out using rat serum for beta 1-3GnT and partially purified enzyme from rat intestine for beta 1-6GnT. beta 1-3GnT has a pH optimum of 7.5 and requires Mn2+ for optimal activity. beta 1-6GnT has a pH optimum of 7.0 and does not require Mn2+. Studies on the substrate specificity of each enzyme indicated that the preferred substrate for beta 1-3GnT had the general structure Gal beta 1-4GlcNAc-OR and, for beta 1-6GnT, Gal beta 1-4GlcNAc beta 1-3Gal-OR where R = sugar. This is the first demonstration that the beta 1-6GnT acts on an internal galactose of lacto-N-neotetraose and paragloboside, and the enzyme appears to be a novel enzyme in terms of substrate specificity.
Gu
J
J
Department of Biochemistry, Osaka University Medical School, Japan.
Nishikawa
A
A
Fujii
S
S
Gasa
S
S
Taniguchi
N
N
D000818:Animals; D000941:Antigens / Q000096:biosynthesis*; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D005964:Glucosyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D007048:I Blood-Group System; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D013058:Mass Spectrometry; D008745:Methylation; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases; D009844:Oligosaccharides / Q000138:chemical synthesis; D009928:Organ Specificity; D051381:Rats; D013379:Substrate Specificity
D000941:Antigens; D007048:I Blood-Group System; D009844:Oligosaccharides; D005964:Glucosyltransferases; D017351:N-Acetylglucosaminyltransferases; C043132:glycosphingolipid beta1-3-N-acetylglucosaminyltransferase; C043131:glycosphingolipid beta1-6-N-acetylglucosaminyltransferase