Lectins
Lectins are complex proteins or glycoproteins that bind specific carbohydrate structures and are therefore able to bind specifically to cells or cell membranes and trigger biochemical reactions from there. However, they do not have any enzymatic activity.
Lectins ( Latin legere , reading ',' select '), various metabolic processes such as cell division , the ribosomal protein biosynthesis , the agglutination of cells (in terms of red blood cells is a hemagglutination ) or the immune system ( Ficoline influence).
Lectins are common. They can be produced by animals, plants or microorganisms.
Classification
The lectins include N- acetylglucosamine -binding Gramineae- lectins, the chitin -binding Solanaceae- lectins, the group of legume lectins and the mannose -binding lectins from Amaryllidaceae , Alliaceae and Orchidaceae . The lectins from Aegopodium podagraria and Urtica dioica have not yet been assigned to any group. Many other lectins are also known.
Lectins also include some AB toxins such as B. high-molecular seed glycoproteins such as ricin or such as the bacterial toxins Shiga toxin , Vero toxin , diphtheria toxin , exotoxin A or alpha-sarcin . Abrin , ricin , phasine (after Phaseolus vulgaris , the common bean : Red kidney bean lectin, erythroagglutinin, PHA-E, Phaseolin ) and IgSF ( English I-type lectins 'I type lectins'), calnexin and calreticulin are different lectins. An example of a lectin without sugar residue is Concanavalin A from the seeds of the jack bean Canavalia ensiformis .
| designation | Organisms | physiological function | particularities | Carbohydrate specificity |
|---|---|---|---|---|
| Abrin | Abrus precatorius | |||
| alpha-sarcin | Aspergillus giganteus mold | Translational inhibition | toxin | |
| Calnexin | Chaperone | |||
| Calreticulin | Chaperone | |||
| Concanavalin A | Jack bean | without sugar residues | α-D-mannosyl and α-D-glucosyl residues | |
| Diphtheria toxin | Corynebacterium diphtheriae | Penetration into cells and translation inhibition | diphtheria | |
| Exotoxin A | Pseudomonas aeruginosa | Penetration into cells | toxin | |
| IgSF | Mammals | |||
| Lentil lectin (LCH) | Lens culinaris | Mannosylated fucose | ||
| Mitogillin | Aspergillus restrictus mold | Translational inhibition | toxin | |
| Phasins | Kidney bean , chickpea | Agglutinins | Hemagglutination , toxin, heat deactivatable | |
| Winterling lectin | Winterling Eranthis hyemalis | Translational inhibition | Type II ribosome-inactivating protein | N-acetyl-D-galactosamine |
| Peanut agglutinin (PNA) | peanut | Galactose -β1-3- N-acetylgalactosamine -α1-Ser / Thr | ||
| Fava Bean Lectin (VFA) | Fava bean | |||
| Hemagglutinin (HA) | Influenza virus | |||
| Elderberry Lectin (SNA) | Black elder | Neu5Ac-α2-6-GalNAc residues | ||
| Jacalin (AIL) | Artocarpus integrifolia | ( Sialic acid ) -Gal-β1-3-GalNAc-α1- serine / threonine | ||
| Maackia amurensis Leucoagglutinin (MAL) | Asian yellow wood | Neu5Ac / Gc-α2-3-Gal-β1-4-GlcNAc | ||
| Maackia amurensis hemoagglutinin (MAH) | Asian yellow wood | Neu5Ac / Gc-α2-3-Gal-β1-3- (Neu5Ac-α2,6) GalNac | ||
| Orange-Red Beaker Lectin (AAL) | Orange-red cup | Fucα1-2Galβ1-4 (Fucα1-3 / 4) Galβ1-4GlcNAc, R2-GlcNAcβ1-4 (Fucα1-6) GlcNAc-R1 | ||
| Phytohemagglutinin (PHA) | Legumes | |||
| Restrictocin | Aspergillus restrictus mold | Translational inhibition | toxin | |
| Ricin (RCA) | wondertree | Seed glycoprotein | Translational inhibition | Galactose -β1-4- N-acetylgalactosamine -β1 residues |
| Robin | Common black locust | |||
| Snowdrop Lectin (GNA) | Little snowdrop | α-1-3 and α-1-6 linked mannose | ||
| Shiga toxin | Shigella dysenteriae | Translational inhibition | Shigellosis | |
| Soybean Lectin (SBA) | Soybean | |||
| Gorse lectins (Gorse, Furze, UEA-I) | Gorse | UEA: Fucα1-2Gal-R | ||
| Vero toxin | Enterohemorrhagic Escherichia coli | Bacterial agitation | ||
| Wheat Germ Lectin (WGA) | wheat | GlcNAc-β1-4-GlcNAc-β1-4-GlcNAc, 5-acetyl- neuraminic acid | ||
| Sweet peas lectin (VVL) | Vicia villosa |
Functions and effects
Effect in nutrition
Lectins of plant origin are found in vegetables, so that the digestive tract of the human lectins is regularly exposed. Some lectins can be toxic to humans or pets in their raw state and only become irreversibly inactivated when they are cooked. Cultivated vegetables (e.g. kidney beans) with such poisonous lectins should only be consumed cooked.
The effect of lectins in the diet, according to some researchers, is to cause them to clump red blood cells. At the end of the 1990s, the naturopathic researcher Peter J. D'Adamo developed a so-called blood group diet based on his research . However, no evidence has yet been found of the supposed health benefits of this diet.
Above a certain amount, some lectins lead to headaches, vomiting, diarrhea as well as stomach and intestinal problems; in extreme cases, consumption can be fatal. In particularly lektinreichen species, such as red beans , already four or five raw seeds can cause serious symptoms in adults. Symptoms of poisoning appear quickly, usually one to three hours after consumption, and usually disappear again just as quickly - about three to four hours after onset.
Antibiotic effect
In their mode of action, lectins are often similar to antibiotics . So Ricin is a potent inhibitor of ribosomal protein biosynthesis. In some cases, lectins have a toxic effect on small organisms and are therefore used as pesticides against insects .
Messenger substances
Lectins are usually attached to the outer membrane surface . They also play a role in the communication and interaction of cells and organisms. For example, they are involved in many recognition processes. With the help of the lectin- polysaccharide interaction, bacteria such as Rhizobium trifolii can attach themselves to the roots of clover . The symbiosis of nodule bacteria and leguminous legumes is only possible with the detection and is therefore specific.
Similar recognition mechanisms play a role in the fertilization of the human egg cell .
germination
Lectins can play a role in ontogenesis . Some plant lectins are inactivated by the germination process .
Chaperones
Examples of lectins are calnexin and calreticulin , which serve as chaperones in protein folding.
purple : glycan, green : protein-carbon, red : oxygen, blue : nitrogen, white : hydrogen
IgSF
More than 500 different proteins of the IgSF - immunoglobulin - family were predicted based on bioinformatic analyzes of mammalian genomes . This includes the Siglec family ( English sialic acid-binding immunoglobulin-type lectins ), a group sialic acid binding lectins.
Found in legumes
The following table shows the lectin content of various legumes (according to the USFDA ):
| variety | Lectin content in hemagglutinating units (HAE) |
|---|---|
| Red kidney beans , raw | 20,000-70,000 |
| White kidney bean, raw | 7,000-23,000 |
| Broad bean , raw | 1,000-7,000 |
| Red kidney beans, well cooked | 200-400 |
Individual evidence
- ↑ a b c Irwin J. Goldstein, Colleen E. Hayes: The lectins: carbohydrate-binding proteins of plants and animals. In: Advances in Carbohydrate Chemistry and Biochemistry. Volume 35, 1978, pp. 127-340. doi: 10.1016 / S0065-2318 (08) 60220-6
- ↑ a b c d Varki Ajit, Paul R. Crocker: I-type lectins. In: A. Varki, RD Cummings, JD Esko et al: Essentials of Glycobiology. 2nd Edition. 2009. PMID 20301278 , chapter 32
- ↑ a b c Patent EP1008852 : Method for the specific detection of glycosylated proteins. Registered on November 15, 1999 , published on September 3, 2003 , applicant: Aventis Behring, inventor: Annette Feussner, Jürgen Römisch.
- ↑ a b c Jacqueline Kupper, Cornelia Reichert: Poisoning with plants . In: Therapeutic review . tape 66 , no. 5 , 2009, p. 343-348 , doi : 10.1024 / 0040-5930.66.5.343 .
- ↑ a b c FDA: Bad Bug Book: Foodborne Pathogenic Microorganisms and Natural Toxins Handbook Phytohaemagglutinin. ( Memento of March 8, 2013 in the Internet Archive )
- ↑ Arpad Pusztai , Susan Bardocz: lectin - Biomedical Perspectives. Taylor & Francis, 2005, ISBN 0-7484-0177-6 , pp. 2ff.
- ↑ MT McConnell, DR Lisgarten, LJ Byrne, SC Harvey, E. Bertolo: Winter Aconite (Eranthis hyemalis) Lectin as a cytotoxic effector in the lifecycle of Caenorhabditis elegans. In: PeerJ. Volume 3, 2015, p. E1206, doi : 10.7717 / peerj.1206 , PMID 26312191 , PMC 4548470 (free full text).
- ↑ Leila Cusack, Emmy De Buck, Veerle Compernolle, Philippe Vandekerckhove: Blood type diets lack supporting evidence: a systematic review. In: Am J Clin Nutr. 98 (1), Jul 2013, pp. 99-104. doi: 10.3945 / ajcn.113.058693 . PMID 23697707 .
- ^ Information center against poisoning: kidney beans
literature
- Rudolf Hänsel, Otto Sticher (Ed.): Pharmakognosie - Phytopharmazie . 9., revised. and updated edition. Springer, Heidelberg 2010, ISBN 978-3-642-00962-4 , Chapter 21: Plant lectins: Occurrence, properties, analysis and evaluation of their immunomodulatory activity , doi : 10.1007 / 978-3-642-00963-1_21 .
- A. Pusztai, S. Bardocz: Biological Effects of Plant Lectins on the Gastrointestinal Tract: Metabolic Consequences and Applications . In: Trends in Glycoscience and Glycotechnology . tape 8 , no. 41 , 1996, pp. 149-165 , doi : 10.4052 / tigg.8.149 .
- Harold Rüdiger: Lectins: Occurrence, Application and Function. In: Chemistry in Our Time . 15th year, No. 5, 1981, pp. 155-162. doi: 10.1002 / ciuz.19810150505
- D. Nelson, M. Cox: Lehninger Biochemie. 4th edition. Springer, Berlin 2011, ISBN 978-3-540-68638-5 , pp. 343-347. doi: 10.1007 / 978-3-540-68638-5
Web links
- Botany online: Lectins ( Memento from December 30, 2011 in the Internet Archive )