Psophocarpus tetragonolobus

About the Lectin

Several research groups have reported isolating lectins from the seeds of Psophocarpus tetragonolobus (winged bean). In 1979 Pueppke reported a method for isolating a lectin using affinity chromatography 1 . The initial seed extracts as well as the purified lectin were reported to agglutinate human erythrocytes, regardless of blood type, only after treatment with neuraminidase or trypsin. This is in direct contrast with results reported by Appukuttan and Basu 2 , and also results obtained by EY Laboratories. The material prepared by EY Laboratories agglutinates untreated human erythrocytes regardless of blood type. Neuraminidase treated cells are agglutinated more readily than untreated cells. The lectin described by Peuppke reacts strongly with β–linked galactose residues while GalNAc has almost no inhibitory activity. Conversely, the lectin purified by Appukuttan and Basu is primarily specific for GalNAc although galactose is inhibitory to a lesser degree. EY Laboratories has isolated a galactose specific and a GalNAc specific lectin from seed extracts using affinity chromatography. When analyzed by SDS-PAGE, the GalNAc specific lectin gives a single band of 27,000 Da, while the galactose specific lectin gives a single band of 29,000 Da. Both lectins are inhibited to some degree by lactose indicating a preference for a β–linked saccharide. Several other researchers have isolated acidic and basic lectins from seeds of the winged bean 3-6 . The lectins with a pI > 9.5 are termed basic lectins while those with a pI=5.5 are termed acidic lectins. Each group appears to be composed of at least 3 isolectins having similar, but not identical N-terminal sequences 5 suggesting that they are products of a multigene family, as in other legumes. Agglutination studies and carbohydrate specificity analysis of the basic lectins indicate that they are not identical to the two lectins supplied by EY Laboratories. The GalNAc specific PTA is most comparable to the acidic lectin, WBA II 4 . By thermodynamic analyses of substitution of N-dansylgalactosamine, the WBA II(GalNAc-binding lectin) was shown to bind 2′ fucosyllactose and H disaccharide (Fucα2Gal) more strongly than lactose or galactose, although fucose itself was non-binding 7 . In addition to the various seed lectins already reported, a lectin from winged bean tubers has also been purified; the carbohydrate specificity has been determined to be similar to that of the seed lectins 8 . The winged bean lectins (acidic and basic) are useful in specifically staining capillaries in human muscle in a serotype-dependent manner 9 .

REFERENCES

  1. Pueppke, S. G. (1979) Biochim. Biophys. Acta. 581 : 63-70.
  2. Appukuttan, P. S. and Basu, D. (1981) Anal. Biochem..113 : 253-255.
  3. Matsuda, T., et al. (1989) Mol. Immunol. 26 : 189-195.
  4. Patanjali, S. R., et al. (1988) Biochem. J. 252 : 625-631.
  5. Kortt, A. A. (1984) Eur. J. Biochem. 138 : 519-525.
  6. Higuchi, M., et al. (1989) J. Nutri. 119 : 490-495.
  7. Acharya, S., et al. (1990) J. Biol. Chem. 265 : 11586-11594.
  8. Shet, M., et al. (1988) Biochim. Biophys. Acta. 954 : 44-49.
  9. Kirkeby, S., et al. (1997) Histochem. Cell Biol. 107 : 31-37.

Product Characteristics

Buffer 0.01M Phosphate – 0.15M NaCl, pH 7.2-7.4.
Blood Group Non-specific. Both lectins react weakly with type A1 erythrocytes.
Activity Less than 0.5 μg/ml of either the galactose specific lectin or the N-acetyl‑D‑galactosamine specific lectin will agglutinate human type O, B, or A2 erythrocytes. Less than 15 μg/ml of N-acetyl‑D‑galactosamine specific PTA will agglutinate type A1 cells. Less than 8 μg/ml of galactose specific PTA will agglutinate type A1 cells.
Inhibitory Carbohydrate Galactose (L-7901). N-acetyl‑D‑galactosamine (L-7902). Lactose will inhibit both lectins.
Molecular Weight 29,000 Da for the galactose specific lectin. 27,000 Da for the N-acetyl‑D‑galactosamine specific lectin. Each lectin gives single band purity by SDS‑PAGE.