Lectin

Source: Wikipedia, the free encyclopedia.
Not to be confused with Leptin or Lecithin.
Lateral hemagglutinine

Lectins are

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 toxins such as ricin.[3]

Lectins may be disabled by specific

genetically engineered crops
to transfer pest resistance.

Etymology

Table of the major plant lectins [4]
  Lectin Symbol Lectin name Source Ligand motif
Mannose-binding lectins
ConA Concanavalin A Canavalia ensiformis 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)

LCH Lentil lectin
Lens culinaris
 Fucosylated core region of bi- and triantennary complex type N-Glycans
GNA Snowdrop lectin Galanthus nivalis α 1-3 and α 1-6 linked high mannose structures
N-acetylgalactosamine
binding lectins
RCA Ricin, Ricinus communis agglutinin, RCA120
Ricinus communis
 Galβ1-4GalNAcβ1-R
PNA Peanut agglutinin
Arachis hypogaea
 Galβ1-3GalNAcα1-Ser/Thr (T-Antigen)
AIL Jacalin
Artocarpus integrifolius
 (Sia)Galβ1-3GalNAcα1-Ser/Thr (T-Antigen)
VVL Hairy vetch lectin Vicia villosa GalNAcα-Ser/Thr (Tn-Antigen)
N-acetylglucosamine
binding lectins
WGA Wheat germ agglutinin Triticum vulgaris GlcNAcβ1-4GlcNAcβ1-4GlcNAc, Neu5Ac (sialic acid)
N-acetylneuraminic acid
binding lectins
SNA Elderberry lectin Sambucus nigra Neu5Acα2-6Gal(NAc)-R
MAL Maackia amurensis leukoagglutinin Maackia amurensis Neu5Ac/Gcα2,3Galβ1,4Glc(NAc)
MAH Maackia amurensis hemoagglutinin Maackia amurensis Neu5Ac/Gcα2,3Galβ1,3(Neu5Acα2,6)GalNac
Fucose binding lectins
UEA Ulex europaeus agglutinin Ulex europaeus Fucα1-2Gal-R
AAL Aleuria aurantia lectin Aleuria aurantia 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[5] introduced the term "lectin" in 1954 from the Latin word lectus, "chosen" (from the verb legere, to choose or pick out).[6]

Biological functions

Lectins may

enzymatic
activity.

blood group
determinant); only a part of the oligosaccharide (central, in grey) is shown for clarity.

Animals

Lectins have these functions in animals:

  • The regulation of cell adhesion
  • The regulation of glycoprotein synthesis
  • The regulation of blood protein levels
  • The binding of soluble extracellular and intercellular glycoproteins
  • As a receptor on the surface of mammalian liver cells for the recognition of galactose residues, which results in removal of certain glycoproteins from the circulatory system
  • As a receptor that recognizes hydrolytic enzymes containing
    mannose-6-phosphate, and targets these proteins for delivery to the lysosomes; I-cell disease
    is one type of defect in this particular system.
  • Lectins are known to play important roles in the innate
    microorganisms. Other immune lectins play a role in self-nonself discrimination and they likely modulate inflammatory and autoreactive processes.[7] Intelectins (X-type lectins) bind microbial glycans and may function in the innate immune system as well. Lectins may be involved in pattern recognition and pathogen elimination in the innate immunity of vertebrates including fishes.[8]

Plants

The function of lectins in plants (legume lectin) is still uncertain. Once thought to be necessary for rhizobia binding, this proposed function was ruled out through lectin-knockout transgene studies.[9]

The large concentration of lectins in plant seeds decreases with growth, and suggests a role in plant

phytohormones.[10]

Lectin receptor kinases (LecRKs) are believed to recognize damage associated molecular patterns (DAMPs), which are created or released from herbivore attack.[citation needed] 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.[citation needed]

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[11]

Bacteria and viruses

Some

glycolipids.[13] Multiple viruses, including influenza and several viruses in the Paramyxoviridae family, use this mechanism to bind and gain entry to target cells.[14]

Use

In medicine and medical research

Purified lectins are important in a clinical setting because they are used for

blood typing.[15]
Some of the glycolipids and glycoproteins on an individual's red blood cells can be identified by lectins.

Non blood-group antigens can be identified by lectins:

  • A lectin from coconut milk is used to identify Theros antigen.
  • A lectin from Carex is used to identify R antigen.

In neuroscience, the

PHA-L, a lectin from the kidney bean.[16]

A lectin (

HIV-1 in vitro.[17] 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.[18]

In studying carbohydrate recognition by proteins

histochemistry of fish muscles infected by a myxozoan

Lectins from legume plants, such as

crystal structures
of legume lectins have led to a detailed insight of the atomic interactions between carbohydrates and proteins.

Legume seed lectins have been studied for their insecticidal potential and have shown harmful effects for the development of pest.[19]

As a biochemical tool

Concanavalin A and other commercially available lectins have been used widely in affinity chromatography for purifying glycoproteins.[20]

In general, proteins may be characterized with respect to

blotting, affinity electrophoresis, and affinity immunoelectrophoreis with lectins, as well as in microarrays, as in evanescent-field fluorescence-assisted lectin microarray.[21]

In biochemical warfare

One example of the powerful biological attributes of lectins is the biochemical warfare agent ricin. The protein ricin is isolated from seeds of the

jequirity pea
is similar:

  • One domain is a lectin that binds cell surface galactosyl residues and enables the protein to enter cells.
  • The second domain is an N-
    glycosidase
    that cleaves nucleobases from ribosomal RNA, resulting in inhibition of protein synthesis and cell death.

Dietary lectin

phytohemagglutinin found in raw Vicia faba
(fava bean).

Lectins are widespread in nature, and many foods contain the proteins. Some lectins can be harmful if poorly cooked or consumed in great quantities. They are most potent when raw as boiling, stewing or soaking in water for several hours can render most lectins inactive. Cooking raw beans at low heat, though, such as in a slow cooker, will not remove all the lectins.[22]

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 inflammatory 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.[22]

Lectin-free diet

Main article: lectin-free diet

The first writer to advocate a lectin-free diet was Peter J. D'Adamo, a naturopathic physician best known for promoting the Blood type diet. He argued that lectins may damage a person's blood type by interfering with digestion, food metabolism, hormones, insulin production—and so should be avoided.[23] D'Adamo provided no scientific evidence nor published data for his claims, and his diet has been criticized for making inaccurate statements about biochemistry.[23][24]

nightshade vegetables: tomatoes, potatoes, eggplant, bell peppers, and chili peppers.[25][26] 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.[27][28][29]

Toxicity

Lectins are one of many toxic constituents of many raw plants that are inactivated by proper processing and preparation (e.g., cooking with heat, fermentation).

allergic) reactions.[31]

Hemagglutination

Lectins are considered a major family of protein

antibodies in their ability to agglutinate red blood cells.[33]

Many legume seeds have been proven to contain high lectin activity, termed hemagglutination.[34] Soybean is the most important grain legume crop in this category. Its seeds contain high activity of soybean lectins (soybean agglutinin or SBA).

History

Long before a deeper understanding of their numerous biological functions, the plant lectins, also known as

fungi and animals)[35] and used in biomedicine for blood cell testing and in biochemistry for fractionation.[citation needed
]

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

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.[36] The legume lectins are probably the most well-studied lectins.

See also

References

  1. PMID 805150
    .
  2. PMID 23573288
    .
  3. PMID 27960074
    .
  4. ^ "Lectin list" (PDF). Interchim. 2010. Retrieved 2010-05-05.
  5. PMID 17842730
    .
  6. S2CID 24989148
    .
  7. PMID 25578468
    .
  8. PMID 23911406
    .
  9. PMID 18444906
    .
  10. PMID 16525538
    .
  11. ^ L.Y. Yatsu, T.J. Jacks, Association of lysosomal activity with aleurone grains in plant seeds, Archives of Biochemistry and Biophysics, Volume 124, 1968, Pages 466-471, ISSN 0003-9861, https://doi.org/10.1016/0003-9861(68)90354-8.
  12. PMID 17428568
    .
  13. PMID 9973330
    .
  14. PMID 12438628
    .
  15. PMID 15229195
    .
  16. ISBN 978-0-205-46724-2
    .
  17. PMID 20080975
    .
  18. S2CID 84825587
    .
  19. S2CID 249145357
    .
  20. ^ "Immobilized Lectin". legacy.gelifesciences.com.[permanent dead link]
  21. ^ Glyco Station, Lec Chip, Glycan profiling technology Archived 2010-02-23 at the Wayback Machine
  22. ^ a b "Lectins". Harvard School of Public Health. 2019-01-24.
  23. ^
    ISBN 0-313-31787-9
  24. ISBN 0-89793-237-4
  25. ^ Rosenbloom, Cara. (2017). "Going 'lectin-free' is the latest pseudoscience diet fad". The Washington Post. Retrieved 25 August 2021.
  26. ^ Amidor, Toby. (2017). "Ask the Expert: Clearing Up Lectin Misconceptions". Today's Dietitian. Vol. 19, No. 10, p. 10. Retrieved December 2021.
  27. Washington Post
    . Retrieved 28 July 2017.
  28. ^ Warner, Anthony (27 July 2017). "Lectin-free is the new food fad that deserves to be skewered". New Scientist. Retrieved 28 July 2017.
  29. ISBN 9780062427137
    .
  30. ^ Taylor, Steve (2008). "40: Food Toxicology (Lectins: Cell-Agglutinating and Sugar-Specific Proteins)". In Metcalfe, Dean; Sampson, Hugh; Simon, Ronald (eds.). Food Allergy: Adverse Reactions to Foods and Food Additives (4th ed.). pp. 498–507.
  31. PMID 10884708
    .
  32. PMID 356549
    .
  33. PMID 5055944
    .
  34. PMID 6769798
    .
  35. ISBN 978-0-471-96445-2
    . Retrieved 18 April 2013.
  36. PMID 33747749
    .

Further reading

External links
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