Studies on the enzymic N-acylation of amino sugars in the sheep colonic mucosa.
1. d-[2-(14)C]Glucose, [2-(14)C]acetate, hydroxy[3-(14)C]pyruvate, [3-(14)C]pyruvate and [U-(14)C]glycine were incorporated by surviving scrapings of sheep colonic mucosal tissue into glycoprotein. 2. d-[2-(14)C]Glucose, [2-(14)C]acetate, incorporated hydroxy-[3-(14)C]pyruvate and [3-(14)C]pyruvate resulted in labelling of each of the monosaccharide residues of the glycoprotein, namely N-glycollylneuraminic acid, N-acetylneuraminic acid, galactose, fucose, glucosamine and galactosamine. [U-(14)C]Glycine was incorporated as glycyl and seryl residues of the glycoprotein. 3. Despite N-glycollylneuraminic acid being quantitatively the predominant sialic acid (N-glycollylneuraminic acid and N-acetylneuraminic acid were 8.5 and 5.2% by weight of the glycoprotein respectively) the corresponding ratio of the radio-active labelling from d-[2-(14)C]glucose in N-glycollylneuraminic acid to that in N-acetylneuraminic acid was 1.00:7.27 (expressed as percentages of the total radioactivity in the glycoprotein). Neutral sugar, hexosamine and N-acetylneuraminic acid residues of the mucoprotein were each labelled to a similar extent. 4. Similarly, the ratio of the radioactivity in N-glycollylneuraminic acid to that in N-acetylneuraminic acid in the mucoprotein from tissue incubations with [2-(14)C]-acetate was 1.0:4.0. 5. Both [2-(14)C]acetate and [2-(14)C]glucose with whole tissue led to labelling of the N-glycollyl substituent and of the main nonose skeleton of the N-glycollylneuraminic acid. In whole-tissue incubations, [3-(14)C]pyruvate was also a precursor of radioactive N-glycollylneuraminic acid. 6. Hydroxy[3-(14)C]-pyruvate and [U-(14)C]glycine caused labelling of the carbohydrate and peptide residues of the glycoprotein, but did not give rise to labelling in the N-glycollylneuraminic acid residues. 7. With a wide variety of possible N-glycollyl precursors (fructose 6-phosphate, hydroxypyruvate, glycollate and chemically synthesized glycollyl-CoA) biosynthesis of N-glycollylglucosamine was not observed in cell-free preparations.
D000085:Acetates / Q000378:metabolism*; D000606:Amino Sugars / Q000378:metabolism*; D000818:Animals; D002247:Carbon Isotopes; D003106:Colon; D005643:Fucose / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D005944:Glucosamine / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D006595:Hexosamines / Q000378:metabolism; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D009438:Neuraminic Acids / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D012756:Sheep
D000085:Acetates; D000606:Amino Sugars; D002247:Carbon Isotopes; D006595:Hexosamines; D009438:Neuraminic Acids; D011773:Pyruvates; D005643:Fucose; D012694:Serine; D005947:Glucose; D005944:Glucosamine; D005998:Glycine; D005690:Galactose