Phytohaemagglutinin
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Phytohaemagglutinin (PHA, or phytohemagglutinin) is a lectin found in plants, especially beans. It is found in the highest concentrations in uncooked red kidney beans (Phaseolus vulgaris), and it is also found in lower quantities in many types of green bean. It 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.
As a toxin it can cause poisoning in monogastric animals, such as humans, through the consumption of raw or improperly prepared kidney beans. Measured in haemagglutinating units (hau) a raw kidney bean can contain up to 70,000 hau. This can be reduced around 200-fold by correct cooking. The bean also contains α-amylase inhibitor.
Poisoning can be induced from as few as five raw beans and symptoms occur within three hours, beginning with nausea then vomiting which can be severe and sustained (profuse), then diarrhea. Recovery occurs within four or five hours of onset, usually without the need for any medical intervention.
Medically it is used as a mitogen to trigger cell division in T-lymphocytes, and to activate latent HIV-1 from human peripheral lymphocytes.
PHA actually consists of two closely related proteins, called PHA-L and PHA-E. The letters E and L point to the fact that these proteins agglutinate Erythrocytes and Leukocytes, respectively.
References
- Hamelryck T, Dao-Thi M, Poortmans F, Chrispeels M, Wyns L, Loris R (1996). "The crystallographic structure of phytohemagglutinin-L". J Biol Chem 271 (34): 20479-85. PMID 8702788.
External links
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
