Phytohaemagglutinin

Legume lectin domain
Crystal structure of PHA-L (PDB 1fat[1])
Identifiers
Symbol	Lectin_legB
Pfam	PF00139
Pfam clan	CL0004
InterPro	IPR001220
PROSITE	PDOC00278
SCOP2	1lem / SCOPe / SUPFAM
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

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.^[2]

It is found in the highest concentrations in uncooked red kidney beans and white kidney beans (also known as cannellini),^[3] and it is also found in lower quantities in many other types of green beans and other common beans (Phaseolus vulgaris), as well as broad beans (Vicia faba) such as fava beans.^[4] It has a number of physiological effects and is used in medical research. In high doses, it is a toxin.^[4]

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.^{[citation needed]}