Lektin

Lectin is a protein that binds to specific carbohydrate structures. Lectins occur in many organisms, but are especially abundant in higher plants. They can cause agglutination of cells and precipitation of glycoconjugates, and are often involved in cell–cell recognition, defense against pests, and immune responses.

In plants, lectins are found in seeds and other tissues. Notable examples include phytohemagglutinin in red kidney beans, concanavalin A from jack beans, and wheat germ agglutinin. Lectins have diverse sugar specificities; some bind glucose or mannose, others bind galactose or sialic acid. Each lectin can be used to detect particular glycan structures in research and diagnostic contexts.

Food safety and nutrition: Some lectins can be toxic if the food is eaten raw or inadequately processed. Phytohemagglutinins in certain beans can cause gastrointestinal symptoms and interfere with nutrient absorption. Most dietary lectins are heat-labile; cooking, soaking, and fermentation reduce activity. Proper preparation of legumes and grains generally renders them safe for consumption. Extremely toxic lectins exist, such as the toxin ricin from castor beans, which is not used as a food and has a separate safety risk.

Applications and research: Lectins are widely used as tools to study carbohydrates. They are employed in histology to map glycans, in glycoprotein purification, and in blood typing. Some researchers explore lectins for therapeutic or diagnostic applications, though safety, specificity, and potential adverse effects remain important considerations. Overall, lectins represent a diverse family of carbohydrate-binding proteins with both practical uses and health considerations.