Phytohaemagglutinin

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Phytohaemagglutinin (PHA, or phytohemagglutinin) is a lectin found in plants, especially certain legumes. PHA actually consists of two closely related proteins, called leucoagglutinin (PHA-L) and PHA-E. These proteins cause blood cells to clump together. PHA-E cause erythrocytes (red blood cells) to clump. PHA-L causes leukocytes (white blood cells) to clump. Phytohaemagglutinin has carbohydrate-binding specificity for a complex oligosaccharide containing galactose, N-acetylglucosamine, and mannose. PHA is found in the highest concentrations in uncooked red kidney beans (Phaseolus vulgaris) and another variety of Phaseolus vulgaris, white kidney beans (also known as cannellini), and it is also found in lower quantities in many other types of common green beans, such as broad beans (Vicia faba) also known as fava beans. PHA has a number of physiological effects and is used in medical research. In high doses, it is a toxin. The lectin has a number of effects on cell metabolism; it induces mitosis, and affects the cell membrane in regard to transport and permeability to proteins. It agglutinates most mammalian red blood cell types.