| Abstrakt: |
The combining site of a GalNA ca1→specific lectin (CFT) with Thomsen-Friedenreich (T.Galβ1→3-GalNAcα1→Ser/Thr) activity, purified from the subspecies tomentosoides of green marine algae Codium fragile ws studied by quantitative precipitin and precipitin-inhibition assays. Of 27 glycoforms tested. Tn (GalNAcβ1&rarrSer/Thr) glycoprotein from armadillo submandibular glands, and asialo porcine submandibular glycoprotein, which contains T. Tn and GalNAcα1→3Gal(A) sequences, completely precipitated the lectin added, and less than 1 μg glycoprotein was required to precipitate 50% 4.7 μg lectin nitrogen. However, CFT precipitated negligibly with Pneumococcus type-XIV polysaccharide and asialo human α1-acid glycoprotein, that contain exclusively the human blood-type-II precursor sequence (II,Galβ1→ 4GlcNAc) at the nonreducing ends. Among the sugar inhibitors tested, the human blood A-active trisaccharide [Ah,GalNAcα1→3(LFuc&alpha:1&rarr2)Gal] was the best inhibitor; it was about twice as active as the T disaccharide. Oligosaccharides without GalNAcα1→ as part of their sequences were inactive, indicating that the ace3tamido group at C2 of galactose is essential for binding and that GalNAc is the main contributor the T sequence for binding. From the data provide, it is clear that the combining site of CFT requires an α-anomer of GalNAc and recognizes Ah, internal GalNAcα1→ of T and Tn determinants of glycans, but not the blood group I/II (Galβ1&rarr3/4GlcNAc) sequences. Consequently, CFT is a useful reagent for detecting GalNAcα1→ containing glycoconjugates. [ABSTRACT FROM AUTHOR] |
