Lectins are carbohydrate-binding that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of and . Lectins have a role in recognition at the cellular and molecular level and play numerous roles in biological recognition phenomena involving cells, carbohydrates, and proteins. Lectins also mediate attachment and binding of bacteria, viruses, and fungi to their intended targets.
Lectins are found in many foods. Some foods, such as beans and grains, need to be cooked, fermented or sprouted to reduce lectin content. Some lectins are beneficial, such as CLEC11A, which promotes bone growth, while others may be powerful such as ricin.
Lectins may be disabled by specific monosaccharides and oligosaccharides, which bind to ingested lectins from grains, legumes, nightshade plants, and dairy; binding can prevent their attachment to the carbohydrates within the cell membrane. The selectivity of lectins means that they are useful for analyzing blood type, and they have been researched for potential use in genetically engineered crops to transfer pest resistance.
α-D-mannosyl and α-D-glucosyl residues branched α-mannosidic structures (high α-mannose type, or hybrid type and biantennary complex type N-Glycans) |
Fucosylated core region of bi- and triantennary complex type N-Glycans |
α 1-3 and α 1-6 linked high mannose structures |
Galβ1-4GalNAcβ1-R |
Galβ1-3GalNAcα1-Ser/Thr (T-Antigen) |
(Sia)Galβ1-3GalNAcα1-Ser/Thr (T-Antigen) |
GalNAcα-Ser/Thr (Tn-Antigen) |
GlcNAcβ1-4GlcNAcβ1-4GlcNAc, Neu5Ac (sialic acid) |
Neu5Acα2-6Gal(NAc)-R |
Neu5Ac/Gcα2,3Galβ1,4Glc(NAc) |
Neu5Ac/Gcα2,3Galβ1,3(Neu5Acα2,6)GalNac |
Fucα1-2Gal-R |
Fucα1-2Galβ1-4(Fucα1-3/4)Galβ1-4GlcNAc, R2-GlcNAcβ1-4(Fucα1-6)GlcNAc-R1 |
William C. Boyd alone and then together with Elizabeth Shapleigh introduced the term "lectin" in 1954 from the Latin word lectus, "chosen" (from the verb legere, to choose or pick out).
The large concentration of lectins in plant seeds decreases with growth, and suggests a role in plant germination and perhaps in the seed's survival itself. The binding of glycoproteins on the surface of parasitic cells also is believed to be a function. Several plant lectins have been found to recognize noncarbohydrate ligands that are primarily hydrophobic in nature, including adenine, auxins, cytokinin, and indole acetic acid, as well as water-soluble porphyrins. These interactions may be physiologically relevant, since some of these molecules function as .
Lectin receptor kinases (LecRKs) are believed to recognize damage associated molecular patterns (DAMPs), which are created or released from herbivore attack. In Arabidopsis, legume-type LecRKs Clade 1 has 11 LecRK proteins. LecRK-1.8 has been reported to recognize extracellular NAD molecules and LecRK-1.9 has been reported to recognize extracellular ATP molecules.
Extraction of proteins and lectins can be extracted via similar processes, also with their analysis, and discovery. For example cottonseed contains compounds of interest within the studies of extraction and purification of proteins L.Y. Yatsu, T.J. Jacks, "Association of lysosomal activity with aleurone grains in plant seeds", Archives of Biochemistry and Biophysics, Vol. 124, 1968, pp. 466–471, , .
A lectin (BanLec) from bananas inhibits HIV-1 in vitro. Achylectins, isolated from Tachypleus tridentatus, show specific agglutinating activity against human A-type erythrocytes. Anti-B agglutinins such as anti-BCJ and anti-BLD separated from Charybdis japonica and Lymantria dispar, respectively, are of value both in routine blood grouping and research.
Legume seed lectins have been studied for their insecticidal potential and have shown harmful effects for the development of pest.
In general, proteins may be characterized with respect to and carbohydrate structure by means of affinity chromatography, blotting, affinity electrophoresis, and affinity immunoelectrophoreis with lectins, as well as in , as in -field fluorescence-assisted lectin microarray. Glyco Station, Lec Chip, Glycan profiling technology
Some studies have found that lectins may interfere with absorption of some minerals, such as calcium, iron, phosphorus, and zinc. The binding of lectins to cells in the digestive tract may disrupt the breakdown and absorption of some nutrients, and as they bind to cells for long periods of time, some theories hold that they may play a role in certain Inflammation conditions such as rheumatoid arthritis and type 1 diabetes, but research supporting claims of long-term health effects in humans is limited and most existing studies have focused on developing countries where malnutrition may be a factor, or dietary choices are otherwise limited.
Steven Gundry proposed a lectin-free diet in his book The Plant Paradox (2017). It excludes a large range of commonplace foods including , legumes, and most fruit, as well as the nightshade vegetables: tomatoes, potatoes, eggplant, bell peppers, and chili peppers.Rosenbloom, Cara. (2017).
Many legume seeds have been proven to contain high lectin activity, termed hemagglutination. Soybean is the most important grain legume crop in this category. Its seeds contain high activity of soybean lectins (soybean agglutinin or SBA).
Although they were first discovered more than 100 years ago in plants, now lectins are known to be present throughout nature. The earliest description of a lectin is believed to have been given by Peter Hermann Stillmark in his doctoral thesis presented in 1888 to the Imperial University of Dorpat. Stillmark isolated ricin, an extremely toxic hemagglutinin, from seeds of the castor plant ( Ricinus communis).
The first lectin to be purified on a large scale and available on a commercial basis was concanavalin A, which is now the most-used lectin for characterization and purification of sugar-containing molecules and cellular structures. The are probably the most well-studied lectins.
Lectin-free diet
target="_blank" rel="nofollow"> "Going 'lectin-free' is the latest pseudoscience diet fad". The Washington Post. Retrieved 25 August 2021.Amidor, Toby. (2017). "Ask the Expert: Clearing Up Lectin Misconceptions". Today's Dietitian. Vol. 19, No. 10, p. 10. Retrieved December 2021. Gundry's claims about lectins are considered pseudoscience. His book cites studies that have nothing to do with lectins, and some that show—contrary to his own recommendations—that avoiding the whole grains wheat, barley, and rye will allow increase of harmful bacteria while diminishing helpful bacteria.
Toxicity
Hemagglutination
History
See also
Further reading
External links
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