Isolation and fractionation of glycopeptides from porcine thyroglobulin

Abstract

1. Glycopeptides were isolated by gel filtration on Sephadex G-25 and Sephadex G-50 from a Pronase digest of porcine thyroglobulin. 2. Isolated glycopeptides were separated into five main fractions on a column of DEAE-Sephadex A-25. Of these fractions I to III were further purified by SE-Sephadex C-25 or DEAE-Sephadex A-25 column chromatography. Several of the purified glycopeptides were homogeneous on paper electrophoresis. 3. Based on the chemical composition and molecular weight of the fractionated glycopeptides, two distinct types of heterosaccharide chain were demonstrated. 4. One type of the heterosaccharide unit consisted of four to eight residues of mannose and two residues of glucosamine and had a molecular weight of 1000-1700. The other type of unit contained sialic acid, fucose and galactose in addition to mannose and glucosamine and had a molecular weight of about 3600. 5. Mild alkaline treatment of the glycopeptide did not result in the destruction of threonine and serine. 2-Acetamido-1-N-(4-l-aspartyl)-2-deoxy-beta-d-glucopyranosylamine was isolated from partial acid hydrolysates.

The Biochemistry of Plant Lectins (Phytohemagglutinins)

“…These lectins belong to two specificity groups, as determined by hapten inhibition studies with simple sugars: Con A and lentil lectin belong to the r~-mannose group; PHA, a Wistaria ltoribunda mitogen having only weak hemagglutinating activity, and a Wistaria [toribunda hemagglutinin free of mitogenie activity, to the N-aeetyl-D-galactosamine group. The inhibitor used by Osawa et al was a glycopeptide of known structure (Figure 2b) obtained from porcine thyroglobulin (275,276). One of the interesting and surprising findings of this study was that enzymic removal of D-galactose (subsequent to the removal of sialic acid) from the glycopeptide caused marked loss in the hemagglutinating inhibitory activity against PHA and the two Wistaria leetins, but did not affect the inhibition of the mitogenie activity of these lectins.…”

Sulfated N‐linked carbohydrate chains in porcine thyroglobulin

“…Concerning the N-linked oligosaccharide chains of porcine thyroglobulin [5,6], the literature data indicate the presence of Mans_9GlcNAc2 structures, whereby the trimming of Man residues seems to take place randomly [7]. For the Nacetyllactosamine type a series of partially sialylated di-(75%) and tri-(25°7o) antennary structures with an crl ,6-1inked Fuc residue at the Asn-bound GlcNAc unit have been reported [8].…”

Structural changes of carbohydrate chains of human thyroglobulin accompanying malignant transformations of thyroid glands

“…Human thyroglobulin was subjected to exhaustive pronase digestion by the method of Fukuda and Egami [16]. To release oligosaccharide moieties from the glycopeptides thus prepared, hydrazinolysis was carried out by the method described previously [14].…”