Preparation of glycopeptides and oligosaccharides from thyroxine-binding globulin.

摘要: Over 99% of thyroxine (T4), the major form thyroid hormone in plasma, is bound to plasma glycoprotein thyroxine-binding globulin (TBG). The carbohydrate composition TBG (14.6% by weight) consists mannose, galactose, N-acetylglucosamine, and N-acetylneuraminic acid molar ratios 11:9:16:10 per mol glycoprotein. No fucose or N-acetylgalactosamine were detected. Amino analyses performed. Glycopeptides, prepared exhaustive pronase treatment glycoprotein, separated gel filtration ion exchange chromatography. All glycopeptides contained four sugars present native One-fourth glycopeptide fraction was resolved into a discrete component, I. remaining mixture termed II III. Glycopeptides III two units, oligosaccharides A B, alkaline-borohydride DEAE-cellulose We propose that contains oligosaccharide chains as calculated from molecular weights compositional data assuming 1 asparagine residue/glycopeptide. structures relative affinities TBG, for hepatocyte membrane binding are presented accompanying paper (Zinn, A.B., Marshall, J.S., Carlson, D.M. (1978) J. Biol. Chem. 253, 6768-6773.