Editing Lectin

{{distinguish|Leptin|Lecithin}}
{{Short description|Carbohydrate-binding protein}}
{{missing information|mapping to Pfam/InterPro of major types|date=May 2019}}
[[File:Hemagglutinin lateral.jpg|thumb|Lateral hemagglutinine]]

'''Lectins''' are [[carbohydrate]]-binding [[protein]]s that are highly specific for sugar [[Moiety (chemistry)|groups]] that are part of other molecules, so cause [[agglutination (biology)|agglutination]] of particular cells or precipitation of [[glycoconjugate]]s and [[polysaccharide]]s. 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.<ref>{{cite journal |author1=URS Rutishauser |author2=Leo Sachs |title=Cell-to-Cell Binding Induced by Different Lectins |journal=Journal of Cell Biology |volume=65 |issue=2 |pages=247–257 |date=May 1, 1975 |doi=10.1083/jcb.65.2.247 |pmid=805150 |pmc=2109424}}</ref><ref>{{cite journal |first1=Matthew |last1=Brudner |first2=Marshall |last2=Karpel |first3=Calli |last3=Lear |first4=Li |last4=Chen |first5=L. Michael |last5=Yantosca |first6=Corinne |last6=Scully |first7=Ashish |last7=Sarraju |first8=Anna |last8=Sokolovska |first9=M. Reza |last9=Zariffard|first10=Damon P.|last10=Eisen |first11=Bruce A. |last11=Mungall |first12=Darrell N. |last12=Kotton |first13=Amel |last13=Omari |first14=I-Chueh |last14=Huang |first15=Michael |last15=Farzan |first16=Kazue |last16=Takahashi |first17=Lynda |last17=Stuart |first18=Gregory L. |last18=Stahl |first19=Alan B. |last19=Ezekowitz |first20=Gregory T.|last20=Spear |first21=Gene G. |last21=Olinger |first22=Emmett V. |last22=Schmidt |first23=Ian C. |last23=Michelow |editor1-first=Bradley S.|editor1-last=Schneider |title=Lectin-Dependent Enhancement of Ebola Virus Infection via Soluble and Transmembrane C-type Lectin Receptors |journal=PLOS ONE |volume=8 |issue=4 |display-authors=10 |doi=10.1371/journal.pone.0060838 |date=April 2, 2013 |pmc=3614905 |pmid=23573288 |pages=e60838 |bibcode=2013PLoSO...860838B |doi-access=free}}</ref> 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 [[toxin]]s such as   [[ricin]].<ref>{{cite journal |title=Lectins bring benefits to bones |doi=10.7554/eLife.22926 |journal=eLife |volume=5 |first1=Charles KF |last1=Chan |first2=Ryan C |last2=Ransom |first3=Michael T |last3=Longaker |date=13 December 2016 |pmc=5154756 |pmid=27960074 |doi-access=free }}</ref>

Lectins may be disabled by specific [[monosaccharides|mono-]] 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.

==Etymology==
{|class="wikitable" style="float:right; font-size:85%; margin-left:15px; width:50%"
! colspan=4 |'''Table of the major plant lectins''' <ref>{{cite web |url=http://www.interchim.fr/ft/M/MS902z.pdf |title=Lectin list |publisher=Interchim |year=2010 |access-date=2010-05-05}}</ref>
|-
!&nbsp; Lectin Symbol !! Lectin name !! Source !! Ligand motif
|-
!colspan=6 |'''[[Mannose]]-binding lectins'''
|-
|'''ConA'''   ||[[Concanavalin A]]   ||''[[Canavalia ensiformis]]''   ||α-D-mannosyl and α-D-glucosyl residues <br />
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
|-
!colspan=4 |'''[[Galactose]] / [[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)
|-
!colspan=4 |'''[[N-acetylglucosamine]] binding lectins'''
|-
|'''WGA'''   ||[[Wheat germ agglutinin]]  ||''[[Wheat|Triticum vulgaris]]''   ||GlcNAcβ1-4GlcNAcβ1-4GlcNAc, Neu5Ac (sialic acid)
|-
!colspan=4 |'''[[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
|-
!colspan=4 |'''[[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, <br />
R2-GlcNAcβ1-4(Fucα1-6)GlcNAc-R1
|}

[[William C. Boyd]] alone and then together with Elizabeth Shapleigh<ref>{{Cite journal |author=Boyd, W.C. |author2=Shapleigh, E. |date=1954 |title=Specific precipitation activity of plant agglutinins (lectins). |journal=Science |volume=119 |issue=3091 |page=419 |doi=10.1126/science.119.3091.419 |pmid=17842730 |bibcode=1954Sci...119..419B}}</ref> introduced the term "lectin" in 1954 from the Latin word ''lectus'', "chosen" (from the verb ''legere'', to choose or pick out).<ref>{{Cite journal |doi=10.1111/j.1365-2559.1985.tb02790.x |pmid=4085980 |title=The use of lectins in histopathology |journal=Histopathology |volume=9 |issue=10 |pages=1121–1124 |year=2007 |last1=Walker |first1=R. |s2cid=24989148}}</ref>

==Biological functions==
Lectins may [[Glycan-protein interactions|bind]] to a soluble carbohydrate or to a carbohydrate [[functional group|moiety]] that is a part of a [[glycoprotein]] or [[glycolipid]]. They typically [[Agglutination (biology)|agglutinate]] certain animal cells and/or precipitate [[glycoconjugate]]s. Most lectins do not possess [[enzymatic]] activity.

[[File:gs4 sugar all.png|thumb|An [[oligosaccharide]] (shown in grey) bound in the binding site of a plant lectin (''[[Griffonia simplicifolia]]'' isolectin IV in complex with the Lewis b [[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 [[lysosome]]s; [[I-cell disease]] is one type of defect in this particular system.
* Lectins are known to play important roles in the innate [[immune system]]. Lectins such as the [[mannose-binding lectin]], help mediate the first-line defense against invading [[microorganisms]]. Other immune lectins play a role in self-nonself discrimination and they likely modulate inflammatory and autoreactive processes.<ref>{{cite journal |vauthors=Maverakis E, Kim K, Shimoda M, Gershwin M, Patel F, Wilken R, Raychaudhuri S, Ruhaak LR, Lebrilla CB |title=Glycans in the immune system and The Altered Glycan Theory of Autoimmunity |journal=J Autoimmun |volume=57 |issue=6 |pages=1–13 |year=2015 |pmid=25578468 |pmc=4340844 |doi=10.1016/j.jaut.2014.12.002}}</ref> [[Intelectin]]s (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.<ref>{{cite journal |doi=10.1016/j.molimm.2013.06.020 |pmid=23911406 |title=Fish lily type lectin-1 contains β-prism architecture: Immunological characterization |journal=Molecular Immunology |volume=56 |issue=4 |pages=497–506 |year=2013 |last1=Arasu |first1=Abirami |last2=Kumaresan |first2=Venkatesh |last3=Sathyamoorthi |first3=Akila |last4=Palanisamy |first4=Rajesh |last5=Prabha |first5=Nagaram |last6=Bhatt |first6=Prasanth |last7=Roy |first7=Arpita |last8=Thirumalai |first8=Muthukumaresan Kuppusamy |last9=Gnanam |first9=Annie J.|last10=Pasupuleti|first10=Mukesh |last11=Marimuthu |first11=Kasi |last12=Arockiaraj |first12=Jesu}}</ref>

===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.<ref>{{Cite journal |title=Coordinating Nodule Morphogenesis with Rhizobial Infection in Legumes |journal=Annual Review of Plant Biology |volume=59 |pages=519–546 |doi=10.1146/annurev.arplant.59.032607.092839 |pmid=18444906 |year=2008 |last1=Oldroyd |first1=Giles E.D. |last2=Downie |first2=J. Allan}}</ref>

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 [[phytohormone]]s.<ref name="pmid16525538">{{cite journal |vauthors=Komath SS, Kavitha M, Swamy MJ |title=Beyond carbohydrate binding: new directions in plant lectin research |journal=Org. Biomol. Chem. |volume=4 |issue=6 |pages=973–988 |date=March 2006 |pmid=16525538 |doi=10.1039/b515446d}}</ref>

Lectin receptor kinases (LecRKs) are believed to recognize damage associated molecular patterns (DAMPs), which are created or released from herbivore attack.{{cn|date=May 2021}} In ''[[Arabidopsis]]'', legume-type LecRKs Clade 1 has 11 LecRK proteins. LecRK-1.8 has been reported to recognize extracellular [[Nicotinamide adenine dinucleotide|NAD]] molecules and LecRK-1.9 has been reported to recognize extracellular [[Adenosine triphosphate|ATP]] molecules.{{cn|date=May 2021}}

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<ref> 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, {{ISSN|0003-9861}}, {{doi|10.1016/0003-9861(68)90354-8}}.</ref>

===Bacteria and viruses===
Some [[hepatitis C]] viral glycoproteins may attach to [[C-type lectin]]s on the host cell surface (liver cells) to initiate infection.<ref>{{cite journal |author=R. Bartenschlager |author2=S. Sparacio |title=Hepatitis C Virus Molecular Clones and Their Replication Capacity in Vivo and in Cell Culture |journal=Virus Research |volume=127 |issue=2 |pages=195–207 |year=2007 |doi=10.1016/j.virusres.2007.02.022 |pmid=17428568}}</ref> To avoid clearance from the body by the [[innate immune system]], pathogens (e.g., [[virus]] particles and [[bacteria]] that infect human cells) often express surface lectins known as [[adhesins]] and [[hemagglutinin]]s that bind to tissue-specific [[glycans]] on host cell-surface glycoproteins and [[glycolipids]].<ref>{{cite journal |pmid=9973330 |pmc=93481 |title=Bacterial adhesins: common themes and variations in architecture and assembly |journal=J Bacteriol |volume=181 |issue=4 |pages=1059–1071 |year=1999 |last1=Soto |first1=GE |last2=Hultgren |first2=SJ |doi=10.1128/JB.181.4.1059-1071.1999}}</ref> Multiple viruses, including [[influenza]] and several viruses in the [[Paramyxoviridae]] family, use this mechanism to bind and gain entry to target cells.<ref>{{Cite journal| doi = 10.1128/JVI.76.24.13028-13033.2002| issn = 0022-538X| volume = 76| issue = 24| pages = 13028–13033| last1 = Takimoto| first1 = Toru| last2 = Taylor| first2 = Garry L.| last3 = Connaris| first3 = Helen C.| last4 = Crennell| first4 = Susan J.| last5 = Portner| first5 = Allen| title = Role of the Hemagglutinin-Neuraminidase Protein in the Mechanism of Paramyxovirus-Cell Membrane Fusion| journal = Journal of Virology| date = 2002| pmid = 12438628| pmc = 136693}}</ref>

==Use==
===In medicine and medical research===
Purified lectins are important in a clinical setting because they are used for [[blood typing]].<ref>{{Cite journal |doi=10.1093/glycob/cwh122 |pmid=15229195 |title=History of lectins: From hemagglutinins to biological recognition molecules |journal=Glycobiology |volume=14 |issue=11 |pages=53R–62R |year=2004 |last1=Sharon |first1=N. |last2=Lis |first2=H |doi-access=free}}</ref> Some of the glycolipids and glycoproteins on an individual's red blood cells can be identified by lectins.
* A lectin from ''[[Dolichos biflorus]]'' is used to identify cells that belong to the A1 blood group.
* A lectin from ''[[Ulex europaeus]]'' is used to identify the H blood group antigen.
* A lectin from ''[[Vicia graminea]]'' is used to identify the N blood group antigen.
* A lectin from ''[[Iberis amara]]'' is used to identify the M blood group antigen.
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 [[anterograde labeling method]] is used to trace the path of [[efferent nerve fiber|efferent]] [[axon]]s with [[PHA-L]], a lectin from the [[kidney bean]].<ref name="Carlson">{{cite book |author=Carlson, Neil R. |title=Physiology of behavior |publisher=Pearson Allyn & Bacon |location=Boston |year=2007 |isbn=978-0-205-46724-2}}{{page?|date=May 2025}}</ref>

A lectin ([[BanLec]]) from bananas inhibits [[HIV-1]] ''in vitro''.<ref>{{cite journal |doi=10.1074/jbc.M109.034926 |pmid=20080975 |title=A Lectin Isolated from Bananas is a Potent Inhibitor of HIV Replication |journal=Journal of Biological Chemistry |volume=285 |issue=12 |pages=8646–8655 |year=2010 |last1=Swanson |first1=M. D. |last2=Winter |first2=H. C. |last3=Goldstein |first3=I. J. |last4=Markovitz |first4=D. M. |pmc=2838287 |doi-access=free}}</ref> 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.<ref>{{cite journal |doi=10.1080/11250003.2010.492794 |title=Prospect for lectins in arthropods |journal=Italian Journal of Zoology |volume=77 |issue=3 |pages=254–260 |year=2010 |last1=Viswambari Devi |first1=R. |last2=Basilrose |first2=M. R. |last3=Mercy |first3=P. D. |s2cid=84825587|doi-access=free }}</ref>

===In studying carbohydrate recognition by proteins===
[[File:Parasite160010-fig2 - Lectins in Paralichthys olivaceus infected by Kudoa septempunctata - Lectin histochemistry.png|thumb|Lectin [[histochemistry]] of fish muscles infected by a [[myxozoa]]n]]
Lectins from legume plants, such as [[Phytohaemagglutinin|PHA]] or [[concanavalin A]], have been used widely as model systems to understand the molecular basis of how proteins recognize carbohydrates, because they are relatively easy to obtain and have a wide variety of sugar specificities. The many [[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.<ref>{{cite journal | doi=10.1016/j.cbpb.2022.110770 | title=Characterization and expression of prohibitin during the mexican bean weevil (Zabrotes subfasciatus, Boheman, 1833) larvae development | date=2022 | last1=Villegas-Coronado | first1=Diana | last2=Guzman-Partida | first2=Ana María | last3=Aispuro-Hernandez | first3=Emmanuel | last4=Vazquez-Moreno | first4=Luz | last5=Huerta-Ocampo | first5=José Ángel | last6=Sarabia-Sainz | first6=José Andre-i | last7=Teran-Saavedra | first7=Nayelli Guadalupe | last8=Minjarez-Osorio | first8=Christian | last9=Castro-Longoria | first9=Reina | last10=Maldonado | first10=Amir | last11=Lagarda-Diaz | first11=Irlanda | journal=Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology | volume=262 | page=110770 | pmid=35644320 | s2cid=249145357 }}</ref>

===As a biochemical tool===
Concanavalin A and other commercially available lectins have been used widely in [[affinity chromatography]] for purifying glycoproteins.<ref>{{cite web |url=http://legacy.gelifesciences.com/webapp/wcs/stores/servlet/catalog/en/GELifeSciences-se/products/AlternativeProductStructure_17334/ |title=Immobilized Lectin |website=legacy.gelifesciences.com }}{{Dead link|date=February 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

In general, proteins may be characterized with respect to [[glycoform]]s and carbohydrate structure by means of [[affinity chromatography]], [[blotting]], [[affinity electrophoresis]], and [[immunoelectrophoresis|affinity immunoelectrophoreis]] with lectins, as well as in [[microarray]]s, as in [[wikt:evanescent|evanescent]]-field fluorescence-assisted lectin microarray.<ref>[http://www.gpbio.jp/english/tech.html Glyco Station, Lec Chip, Glycan profiling technology] {{webarchive |url=https://web.archive.org/web/20100223005811/http://www.gpbio.jp/english/tech.html |date=2010-02-23 }}</ref>

===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 [[castor oil plant]] and comprises two [[protein domains]]. [[Abrin]] from the [[Rosary pea|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==
[[File:Phytohemagglutinin L.png|thumb|right|Leucoagglutinin is a toxic [[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.<ref name=harvard>{{cite web |title=Lectins |url=https://www.hsph.harvard.edu/nutritionsource/anti-nutrients/lectins/ |publisher=Harvard School of Public Health |date=2019-01-24}}</ref>

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|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.<ref name=harvard/>

===Lectin-free diet===
{{main|lectin-free diet}}
The first writer to advocate a lectin-free diet was Peter J. D'Adamo, a [[Naturopath]] 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.<ref name="Goldstein">Goldstein, Myrna Chandler. (2002). ''Controversies in Food and Nutrition''. Greenwood Press. pp. 221–222. {{ISBN|0-313-31787-9}}</ref> D'Adamo provided no scientific evidence nor published data for his claims, and his diet has been criticized for making inaccurate statements about biochemistry.<ref name="Goldstein"/><ref>Stare, Fredrick John; Whelan, Elizabeth M. (1998). ''Fad-Free Nutrition''. Hunter House Inc. pp. 209–212. {{ISBN|0-89793-237-4}}</ref>

[[Steven Gundry]] proposed a lectin-free diet in his book ''The Plant Paradox'' (2017). It excludes a large range of commonplace foods including [[whole grain]]s, legumes, and most fruit, as well as the [[nightshade vegetable]]s: tomatoes, potatoes, eggplant, bell peppers, and chili peppers.<ref name="Rosenbloom">Rosenbloom, Cara. (2017). [https://archive.today/20191217213222/https://www.washingtonpost.com/lifestyle/wellness/going-lectin-free-is-the-latest-pseudoscience-diet-fad/2017/07/05/45382462-5b4e-11e7-a9f6-7c3296387341_story.html "Going 'lectin-free' is the latest pseudoscience diet fad"]. ''The Washington Post''. Retrieved 25 August 2021.</ref><ref>Amidor, Toby. (2017). [https://www.todaysdietitian.com/newarchives/1017p10.shtml "Ask the Expert: Clearing Up Lectin Misconceptions"]. ''Today's Dietitian''. Vol. 19, No. 10, p. 10. Retrieved December 2021.</ref> 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.<ref name="WapoDiet">{{cite news |url=https://www.washingtonpost.com/lifestyle/wellness/going-lectin-free-is-the-latest-pseudoscience-diet-fad/2017/07/05/45382462-5b4e-11e7-a9f6-7c3296387341_story.html |title=Going 'lectin-free' is the latest pseudoscience diet fad |date=7 July 2017 |access-date=28 July 2017 |newspaper=[[Washington Post]] |first=Cara |last=Rosenbloom}}</ref><ref name="NSDiet">{{cite magazine |url=https://www.newscientist.com/article/2142007-lectin-free-is-the-new-food-fad-that-deserves-to-be-skewered/ |title=Lectin-free is the new food fad that deserves to be skewered |first=Anthony |last=Warner|author-link=Anthony Warner (chef) |magazine=[[New Scientist]] |date=27 July 2017 |access-date=28 July 2017}}</ref><ref>{{Cite book |url=https://nutritionstudies.org/the-plant-paradox-by-steven-grundy-md-commentary |title='The Plant Paradox' by Steven Gundry MD – A Commentary |author1=T. Colin Campbell |author2=Thomas Campbell |publisher=Harper |date=23 August 2017 |isbn=9780062427137}}</ref>

==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).<ref>{{cite book |title=Food Allergy: Adverse Reactions to Foods and Food Additives |editor1-last=Metcalfe |editor1-first=Dean |editor2-last=Sampson |editor2-first=Hugh |editor3-last=Simon |editor3-first=Ronald |chapter=40: Food Toxicology (Lectins: Cell-Agglutinating and Sugar-Specific Proteins) |pages=498–507 |year=2008 |last1=Taylor |first1=Steve |edition=4th}}</ref> For example, raw [[kidney bean]]s naturally contain toxic levels of lectin (e.g. [[phytohaemagglutinin]]). Adverse effects may include [[nutritional deficiencies]], and [[immune reaction|immune]] ([[allergic reaction|allergic]]) reactions.<ref>{{cite journal |doi=10.1017/S0007114500000271 |pmid=10884708 |title=Modulation of immune function by dietary lectins in rheumatoid arthritis |journal=British Journal of Nutrition |volume=83 |issue=3 |pages=207–217 |year=2007 |last1=Cordain |first1=Loren |last2=Toohey |first2=L. |last3=Smith |first3=M. J. |last4=Hickey |first4=M. S. |doi-access=free}}</ref>

===Hemagglutination===
Lectins are considered a major family of protein [[antinutrients]], which are specific sugar-binding proteins exhibiting reversible carbohydrate-binding activities.<ref>{{cite book |doi=10.1016/S0065-2318(08)60220-6 |pmid=356549 |title=The Lectins: Carbohydrate-Binding Proteins of Plants and Animals |volume=35 |pages=127–340 |year=1978 |last1=Goldstein |first1=Erwin |last2=Hayes |first2=Colleen |series=Advances in Carbohydrate Chemistry and Biochemistry |isbn=978-0-12-007235-4}}</ref> Lectins are similar to [[antibodies]] in their ability to agglutinate red blood cells.<ref>{{cite journal |title=Lectins: Cell-Agglutinating and Sugar-Specific Proteins |journal=Science |volume=177 |issue=4053 |pages=949–959 |year=1972 |last1=Sharon |first1=Nathan |last2=Lis |first2=Halina |doi=10.1126/science.177.4053.949 |pmid=5055944 |bibcode=1972Sci...177..949S}}</ref>

Many legume seeds have been proven to contain high lectin activity, termed [[hemagglutination]].<ref>{{cite journal |title=Sialidase-Enhanced Lectin-Like Mechanism for ''Actinomyces viscosus'' and ''Actinomyces naeslundii'' Hemagglutination |journal=Infection and Immunity |volume=27 |issue=2 |pages=335–343 |year=1980 |last1=Ellen |first1=R.P. |last2=Fillery |first2=E.D. |last3=Chan |first3=K.H. |last4=Grove |first4=D.A. |doi=10.1128/IAI.27.2.335-343.1980 |pmid=6769798 |pmc=550769 |doi-access=free}}</ref> [[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 [[phytohemagglutinins]], were noted for their particularly high specificity for foreign [[glycoconjugate]]s (e.g., those of [[fungi]] and animals)<ref>{{cite book |author=Els. J. M. Van Damme |author2=Willy J. Peumans |author3=llArpad Pusztai |author4=Susan Bardocz |title=Handbook of Plant Lectins: Properties and Biomedical Applications |pages=7–8 |publisher=John Wiley & Sons |date=March 30, 1998 |isbn=978-0-471-96445-2 |url=https://books.google.com/books?id=qfkkXIcEO4YC&q=lectin+binding+monosaccharides&pg=PA7 |access-date=18 April 2013}}</ref> and used in biomedicine for blood cell testing and in biochemistry for [[fractionation]].{{citation needed|date=May 2018}}

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 [[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.<ref>{{cite journal |last1=Aksakal |first1=R. |last2=Mertens |first2=C. |last3=Soete |first3=M. |last4=Badi |first4=N. |last5=Du Prez |first5=F. |title=Applications of Discrete Synthetic Macromolecules in Life and Materials Science: Recent and Future Trends |journal=Advanced Science |year=2021 |volume=2021 |issue=2004038 |pages=1–22 |doi=10.1002/advs.202004038 |pmid=33747749 |pmc=7967060 |doi-access=free}}</ref> The [[legume lectin]]s are probably the most well-studied lectins.

==See also==
* [[Glycan-protein interactions]]
* ''[[Bacillus thuringiensis]]''
* [[Lectin pathway]], [[ficolin]]
* [[Toxalbumin]]

==References==
{{Reflist}}

==Further reading==
{{refbegin}}
* {{cite book |author1=Halina Lis |author2=Sharon, Nathan |title=Lectins |edition=Second |publisher=Springer |location=Berlin |year=2007 |isbn=978-1-4020-6605-4}}
* {{Cite journal |vauthors=Ni Y, Tizard I |title=Lectin-carbohydrate interaction in the immune system |journal=Vet Immunol Immunopathol |volume=55 |issue=1–3 |pages=205–223 |year=1996 |pmid=9014318 |doi=10.1016/S0165-2427(96)05718-2}}
{{refend}}

==External links==
* [http://www.bio-world.com/glycobiology/lectins.html Major Lectins & Conjugated Lectins from different natural sources]
* [http://www.functionalglycomics.org/ Functional Glycomics Gateway], a collaboration between the [[Consortium for Functional Glycomics]] and [[Nature Publishing Group]]
* [http://www.proteopedia.org/wiki/index.php/Main_Page Proteopedia shows more than 800 three-dimensional molecular models of lectins, fragments of lectins and complexes with carbohydrates]
* [http://www.eylabs.com/ EY Laboratories, Inc., Lectin and Lectin Conjugates manufacturer]
* [http://www.gelifesciences.com/handbooks Recombinant Protein Purification Handbook] {{Webarchive|url=https://web.archive.org/web/20081205061748/http://www.gelifesciences.com/handbooks |date=2008-12-05 }}
* [http://legacy.gelifesciences.com/webapp/wcs/stores/servlet/CategoryDisplay?categoryId=11449&catalogId=10101&productId=&top=Y&storeId=11253&langId=-1 Immobilized lectins, chromatography media]{{Dead link|date=February 2023 |bot=InternetArchiveBot |fix-attempted=yes }}
* [http://www.medicago.se/ Medicago AB, Lectin and Lectin Conjugates manufacturer]
* Con A {{en:Proteopedia|1bxh}}, pokeweed lectin {{Proteopedia|1uha}}, ''Artocarpus'' lectin {{Proteopedia|1toq}}, ''Pterocarpus'' lectin  {{Proteopedia|1q8v}}, ''Urtica'' lectin  {{Proteopedia|1en2}}

{{Lectins}}

[[Category:Immunology]]
[[Category:Carbohydrates]]
[[Category:Proteins]]
[[Category:Glycoproteins]]
[[Category:Lectins|Lectins]]