Peanut (Arachis hypogaea) lectin: Use in quantitation of desialylation of glycoproteins

A high affinity lectin from an easily available source, peanut (Arachis hypogaea) agglutinin (PNA) which specifically recognizes desialylated versions of sialylated oligosaccharides is a unique tool in glycoconjugate biotechnology. By a single step affinity chromatography on cross-linked guar galactomannan, PNA was purified to homogeneity with 19 times higher hemagglutinating activity than the sample prepared by existing methods involving defatting with organic solvents. Agglutinating activity of the new preparation remained unchanged for at least 6 months while PNA prepared from defatted seed lost activity within one week. Glycoproteins desialylated to varying degrees were prepared by treating bovine fetuin with 0.1 N H2SO4 at 80 degreesC for durations of 10 seconds and above. Enzyme-linked lectin assay of desialylation of differentially desialylated glycoproteins coated on microplates, using horse radish peroxidase (HRP) conjugate of PNA (PNA-HRP), along with sialic content assay revealed that PNA can be used as a quantitative probe for assay of desialylation in sialylated glycoproteins

ANOMER SPECIFICITY OF THE 14-KDA GALACTOSE-BINDING LECTIN - A REAPPRAISAL

A beta-anomer preference among galactosides has been attributed to the S-type 14 kDa galactose binding lectin. Here the anomeric preference of this lectin from bovine brain (BBL) is reexamined using inhibition of lectin-mediated haemagglutination, binding of the lectin to dot-blotted glycoproteins and affinity electrophoresis of the lectin through polysaccharide-containing gels. 1-O-methyl alpha-D-galactoside was 8 times better inhibitor of BBL than the corresponding beta-anomer. The terminal galactose in bovine thyroglobulin (exclusively alpha-linked) were also nearly 8 times more inhibitory than those in asialofetuin (exclusively beta-linked). The terminal alpha-galactose-containing endogenous glycoproteins of bovine brain were nearly 4 times better inhibitors of BBL than laminin. Removal of terminal alpha-galactose units by alpha-galactosidase fully abolished the BBL binding of thyroglobulin and endogenous glycoproteins. BBL was also sugar-specifically retarded by polyacrylamide gel containing guar galactomannan which bears only alpha-linked galactose. Data indicated that alpha-galactosides were sometimes better than their beta-anomers in binding to BBL. The significance of this observation to the physiological role of galactose-binding lectins is discussed