Involvement of sulfhydryl groups in the activity of anti-A hemagglutinins of Phaseolus lunatus

Purification and cDNA cloning of a lectin and a lectin-like protein from Apios americana Medikus tubers

“…20) This cysteine residue is essential for carbohydrate binding because chemical modification of the residue has been found to induce inactivation of activity, and this modification is inhibited in the presence of GalNAc. 21) On the other hand, replacement of the residue in LBL by a Tyr residue altered the carbohydrate specificity of the lectin, and thus the human type-A trisaccharide specificity was lost. 22) If the role of the cysteine residue in AAL is similar to that in LBL, chemical modification or mutagenesis of the residue in AAL might affect oligosaccharide specificity.…”

The Biochemistry of Plant Lectins (Phytohemagglutinins)

“…SH reagents inhibit the hemagglutinating activity of the lima bean lectins with a concurrent loss of protein SH groups (118). N-Acetyl-D-galactosamine, a specific and reversible inhibitor of the lectin (see below), offers protection against inactivation by SH reagents and simultaneously protects some of the SH groups.…”

“…Of these, one is a free SH while the other is involved in an interchain disulfide linkage between two subunits (118). It has been suggested that the lima bean isolectins are a tetramer and dimer of the 60,000 dalton disulfide-containing subunit, although once separated, the two isolectins do not appear to be interconvertible.…”

Phytohemagglutinins. Their nutritional significance

“…It is evident from a comparison of their properties (Table III) that the lectins isolated from different varieties of P. vulgaris are very similar and resemble the soybean hemagglutinin with respect to size, composition, and subunit structure. The lima bean lectin, on the other hand, consists of a greater number of subunits, each of which appears to contain a free sulfhydryl group which seems to be located at the saccharide-binding site (Gould and Scheinberg, 1970).…”