lectin

Lectins are a diverse group of proteins that bind specific carbohydrate structures. Unlike enzymes or antibodies, lectins are non-enzymatic, non-immunoglobulin proteins that recognize and reversibly bind particular sugars or glycan motifs present on the surfaces of cells and glycoproteins. They occur in many organisms, but are particularly abundant in plants, especially seeds, kernels, and tubers. They also occur in some bacteria, fungi, and animals.

In plants, lectins are believed to play roles in defense against pests and pathogens by binding to carbohydrate components of invading organisms or gut tissues of herbivores. Notable plant lectins include phytohemagglutinin in red kidney beans and concanavalin A from jack beans. Some lectins can cause red blood cell agglutination and other physiological effects if consumed raw or improperly cooked, whereas others function mainly as research reagents.

Health and culinary aspects: many dietary lectins are inactivated by heat, soaking, and other processing steps. Raw kidney beans contain high levels of phytohemagglutinin and can cause severe gastrointestinal distress; boiling beans for at least 10 minutes and pressure cooking markedly reduces lectin activity. Overall, diets incorporating properly prepared plant foods with lectins are widely considered safe, though individuals with certain gastrointestinal disorders may have heightened sensitivity. The notion that all lectins are broadly dangerous is oversimplified.

Applications: in the laboratory, lectins are valuable tools for glycobiology. They are used to detect specific sugar moieties, to purify glycoproteins via affinity chromatography, and in histochemical labeling to map glycans in tissues.