About the Lectin
Common lentil seeds contain two isolectins which are almost indistinguishable and which agglutinate erythrocytes from several animal species. The two isolectins, termed LcH-A and LcH-B, are each tetramers composed of two dissimilar subunits. The α- subunit has a MW=5,700 while the larger β- subunit has a MW=17,500 1 . All lentil seeds have been reported to contain both of the isolectins, although not always in the same proportion. The lentil lectin has been purified using a number of different procedures. These include ion-exchange chromatography, and affinity chromatography on a number of different affinity resins. The purified lectin has the same biochemical characteristics regardless of the isolation method used. Purified LcH A and LcH B can be obtained by ion-exchange chromatography of the affinity purified lectin 2 . The only difference is the presence of additional Lys residues on the LcH B a chains due to differences in posttranslational C-terminal cleavage. 3 X-ray crystal structures of the lectin with carbohydrate ligands have been determined. 4 The lentil lectin has a nominal specificity for mannose and glucose. Although LcH and Con A have the same nominal specificity, LcH is less active than Con A when comparing carbohydrates known to specifically inhibit the jack bean lectin. Analysis of the binding properties of LcH indicates that a fucose residue attached to the asparagine linked GlcNAc residue of complex oligosaccharides plays an important role in lectin binding 3 . This specificity is also shared by the lectin from Pisum sativum (PSA), but not by Con A. Both LcH isolectins will bind to glycoconjugates containing Makela’s group III sugars. They also bind to lymphocytes in culture and are mitogenic for these cells. The isolectins have been used to detect different molecular species of human alpha fetoprotein 6,7 , which has been exploited in the diagnosis of hepatocellular carcinoma. 8 Although the lentil and pea lectins are virtually identical, recent communications to EY Laboratories indicate that some glycoconjugates may react strongly with one of the lectins, but not the other. Subtle differences in carbohydrate affinity have been shown to exist between LcH and PSA 8 .
- Foriers, A., et al. (1981) J. Biol. Chem. 256 : 5550-5560.
- Howard, I. K., et al. (1971) J. Biol. Chem. 246 : 1590-1595.
- Young, N.M., et al. (1996) Glycoconj. J. 13 : 575-583.
- Casset, F., et al. (1995) J. Biol. Chem. 270 : 25619-25628.
- Kornfeld, K., et al. (1981) J. Biol. Chem. 256 : 6633.
- Taketa, K., et al. (1985) Electrophoresis. 6 : 492-497.
- Taketa, K. (1987) Electrophoresis. 8 : 409-414.
- Wang, S.S., et al. (1996) J. Hepatology 25 : 166-171.
- Debray, H., et al. (1981) Eur. J. Biochem. 117 : 41-55.
|Buffer||0.05M Tris – 0.15M NaCl, pH 7.0-7.2.|
|Activity||50-200 μg/ml will agglutinate type O human erythrocytes. 2-5 μg/ml will agglutinate neuraminidase treated cells.|
|Inhibitory Carbohydrate||D-Mannose and D-Glucose. A fucose linked α(1,6) to the core GlcNAc of N-linked glycopeptides is an important determinant for lectin activity.|
|Molecular Weight||39-44,000 Da by gel filtration. 20‑25,000 Da in dissociating solvents. 48‑51,000 Da by sedimentation equilibrium. A single band of 20‑28,000 Da by SDS‑PAGE performed at EY Laboratories.|