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Phaseolus vulgaris agglutinin is the name ascribed to a family of lectins, each of which consists of four subunits. There are two different types of subunits. One appears to be involved primarily in red cell agglutination and has been designated the “E” subunit (for erythroagglutinin). The other type is involved in lymphocyte agglutination and mitogenic activity and has been termed the “L” subunit (for leucoagglutinin). These subunits combine to produce five isolectins.
One of these isolectins has four “E” subunits and is designated PHA-E. PHA-E possesses strong hemagglutinating activity but is a poor mitogen. PHA-L, with four “L” type subunits, does not agglutinate red cells but is a potent mitogen. The other three isolectins, designated E3L1, E2L2, and E1L3, have erythroagglutinating and mitogenic activities proportional to the number of respective “E” or “L” subunits. We have termed the mixture of the five isolectins PHA (E+L). All of these isolectins are glycoproteins with molecular weights of approximately 125,000 and have isoelectric points between pH 5.2 for PHA-L and pH 6.0 for PHA-E. |