Heme polymerization pathway (Plasmodium falciparum) (HPP)

The heme polymerization pathway is a critical detoxification process in the Plasmodium falciparum parasite, occurring within its acidic digestive vacuole (Coronado et al., 2014, Biochimica et Biophysica Acta). During the intraerythrocytic stage of its life cycle, the parasite ingests and degrades host hemoglobin to obtain essential amino acids, a process that releases large quantities of free heme (Fe-protoporphyrin IX) (Slater and Cerami, 1992, Nature). This free heme is highly toxic as it generates reactive oxygen species and disrupts cellular membranes; to survive, the parasite polymerizes it into an insoluble, chemically inert crystalline form known as hemozoin (Egan, 2008, Journal of Chemical Biology). This biocrystallization process is facilitated by the Heme Detoxification Protein (HDP) and potentially other lipids within the vacuole (Jani et al., 2008, PNAS). This pathway is the primary target for several classes of antimalarial drugs, most notably the quinolines like chloroquine and quinine, which bind to heme or the growing crystal face to prevent further polymerization (Sullivan et al., 1996, Science). The resulting accumulation of toxic heme monomers leads to parasite death via oxidative stress and membrane lysis (Egan, 2008, Journal of Chemical Biology).

Other names

Heme detoxification pathwayHemozoin formation pathwayFerriprotoporphyrin IX polymerizationHeme biocrystallization

Inhibition of heme biocrystallization into hemozoin, resulting in the accumulation of toxic free ferriprotoporphyrin IX complexes that cause oxidative damage and parasite death.