About the Lectin

Extracts of the slug, Limax flavus, were reported to contain a non-specific blood agglutinin as early as 1970. Carbohydrate inhibition studies have shown that the lectin from Limax flavus has a specificity for sialic acid. Sialic acid is a generic term for more than 20 derivatives of N-acetylneuraminic acid (Neu5Ac) and N-glycolyl- neuraminic acid (Neu5Gc). It has been reported that the agglutination activity of crude extracts of LFA can be inhibited to some degree by several different carbohydrates, however, affinity purified LFA is only inhibited by Neu5Ac and Neu5Gc 1,2 . Experiments performed at EY Laboratories with the related slug, Limax maximus, indicate that the purified form of this lectin is inhibited to some degree by several different carbohydrates. LFA is closest to LPA with respect to its ability to bind different forms of sialic acid. Regardless of the glycosidic linkage, both lectins bind sialic acids; however, LPA may also react with N-acetyl-D-glucosamine and D-glucuronic acid. Other sialic acid specific lectins will generally recognize only specific glycosidic linkages of sialic acid, or have other primary carbohydrate specificities. Since LFA binds to sialic acid regardless of the linkage, and since the lectin does not require additional ions for binding, it offers a number of advantages over other lectins in the study of glycoconjugates. A comprehensive study 3 of the LFA binding specificity indicates a marked preference for the α-ketosidic configuration at C-2, an obligate N-acetamido group at C-5, and tolerance for a substituted hydroxyl group at C-4. The purified lectin is stable in lyophilized form, or when reconstituted and stored at concentrations of 1mg/ml or less. LPA and CCA are much less stable than LFA and cannot be lyophilized for long term storage. Purified LFA has been used successfully in a number of different applications. These include the separation of subpopulations of cells expressing varying degrees of sialylation by FACS and the purification of glycoconjugates containing sialic acid residues by affinity chromatography. Using high-resolution cytochemical techniques involving LFA in conjugation with a fetuin-gold complex and horseradish peroxidase-conjugated LFA, Wagner and Roth demonstrated the presence of sialylated glycoconjugates in developing rat glomeruli 4 , and Hedmen st al. in the trans Golgi stacks of 3T3 cells. 5 Additional information regarding sialic acid and related products may be found in reference 6 and 7.

NOTE: There are no commercial sources for the slug, which must be collected by hand. With the periodic drought conditions in California, the purified lectin may not always be available. Please inquire.

REFERENCES

  1. Miller, R. L. (1982) J. Biol. Chem. 257 : 7574-7580.
  2. Miller, R. L. (1987) Meth. Enzymol. 138 : 527-536.
  3. Knibbs, R.N., et al. (1993) J. Biol. Chem. 268 : 18524-18531.
  4. Wagner, P. and Roth, J. (1998) Eur. J. Cell Biol. 47 : 259-269.
  5. Hedman, K., et al. (1986) J.Histochem. Cytochem. 34 : 1069-1077.
  6. Biotechs: Sialic Acid and Related Products. Summer 1991.EY Laboratories, Inc.
  7. Biotechs: Product Highlights, Sialic Acid & Related Products. EY Laboratories, Inc.

Product Characteristics
Buffer Stored in 0.05M Tris – 0.3M NaCl, pH 7.5.
Blood Group Nonspecific.
Activity 10-15 μg/ml will agglutinate type O human erythrocytes.
Inhibitory Carbohydrate N‑acetylneuraminic acid and N‑glycolylneuraminic acid.
Molecular Weight 44,000 Da by gel filtration A single band of 20,000 Da by SDS-PAGE.
Caution High protein concentrations or the absence of salts will tend to cause aggregation of the lectin. Use the appropriate buffer at all times.