Goldstein et al. [Nature (Lond.) 285, 86 (1980)] have presented the following definition and comments.
Definition
A lectin is a sugar-binding protein of non-immune origin that agglutinates cells or precipitates glycoconjugates.
Comments
1. A lectin molecule contains at least two sugar-binding sites; sugar-binding proteins with a single site will not agglutinate or precipitate structures that contain sugar residues, so are not classified as lectins.
2. The specificity of a lectin is usually defined by the monosaccharides or oligosaccharides that are best at inhibiting the agglutination or precipitation the lectin causes.
3. Lectins occur in many types of organism; they may be soluble or membrane-bound; they may be glycoproteins.
4. Sugar-specific enzymes, transport proteins and toxins may qualify as lectins if they have, multiple sugarbinding sites.
1. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN), and Nomenclature Commission of IUB (NC-IUB),.Newsletter 1981, Arch. Biochem. Biophys., 1981, 206, 458-462; Eur. J. Biochem., 1981, 114, 1-4; Hoppe-Seyler's Z. Physiol. Chem., 1981, 362, I-IV; J. Biol. Chem., 1981, 256, 12-14.