Fractionated Pisum sativum lectin or agglutinin (PSA) is a heterodimer that consists of four subunits. It has a carbohydrate specificity towards Î±-linked mannose-containing oligosaccharides. Itâ€™s hemagglutinating activity can be inhibited by glucose, mannose, and sucrose. It does not have a blood group specificity. The N-terminal sequence of the lectin has shown some degree of homology compared to lectins from other legume species. Pisum sativum lectin has also shown mitogenic effect toward murine splenocytes and could inhibit activity of HIV-1 reverse transcriptase. PSA is often used to differentiate virally transformed from normal cells. Calcium and manganese ions are required for activity.