“Lectin” word originated from latin word “legree” which means “to select”. Lectins are proteins or glycoproteins that have at least one noncatalytic domain that binds specifically and reversibly to monosaccharides or oligosaccharides. Lectins whose sugar specificities are unknown are called hemagglutinins. Lectins are present in every organisms and are involved in biological functions such as adhesive, defence against pathogens, immunomodulatory and regulatory.
Applications of lectins
Due to their diverse roles, lectins are essential in many areas including science, medicine, pharmaceutical companies, biotechnology and other technologies. Some possible/ongoing practical applications of lectins depending upon their functions are:
Use as pesticide (anti-insect activity)
Lectins play an important role against insect pests and therefore had been incorporated in various plants including wheat, rice tobacco and potatoes to create transgenic plants which are resistant to pest attack. Use of lectin as pesticide or transgenic plants with lectins is beneficial for environment as this would reduce the use of chemical pesticides. Lectins exhibit anti-insect activity by increasing mortality or delay in the development of insect.
Use as fungicide (anti-fungal activity)
Some of the lectins and hemagglutinins show anti-fungal activity such as the lectin from Amaranthus virdis (Green Amaranth) seeds. It is shown that the one of the mode of action of lectin as antifungal is to bind to carbohydrates present on fungal wall and impede fungal growth.
Use as a drug for cancer (anti-tumor activity)
There are several lectins that display anti-tumor activity. Lectins elicit apoptois in different cancer cell lines by activating caspase 3 and other caspases. Lectins react with death receptors, FAS receptors expressed on cancer cells to initiate apoptosis.
Use as anti-viral drug
Lectins such as concanavalin A, wheat germ agglutinin, Vicia fava agglutinin and Pisum sativum agglutinin bind to mannose rich gp120 on human immunodeficiency virus (HIV) envelope and inhibit its fusion with CD4 cells. The mode of action may vary for other lectins that display antiviral activity.
Lectin affinity chromatography
In lectin affinity chromatography, the lectins are immobilized on column and used to purify glycoproteins, carbohydrates, or glycolipids. For example concanavalin A lectin is used to isolate mannose glycan rich glycoproteins.
Lectins serve as markers for blood grouping
Different blood groups erythrocytes express specific sugar heads on their surface. Lectins being sugar specific serve as antigenic determinant of blood groups. For example, lectin from Dolicus biflorus can be used for typing ant-A1 blood group.
