Histidine-rich protein II (HRP II) (primary mediator of heme polymerization in P. falciparum) (HRP II)

Plasmodium falciparum digests host hemoglobin during its blood-stage infection, releasing free heme, which is toxic to the parasite. This free heme is detoxified by its protein-mediated polymerization into crystalline hemozoin (malaria pigment), a process primarily catalyzed by histidine-rich proteins such as HRP II and HRP III within the parasite's acidic digestive vacuole[7][4]. This pathway is not mediated by a conventional heme polymerase enzyme[7]. The formation of hemozoin is essential for parasite survival and is a key therapeutic target of several antimalarial drugs, which work by inhibiting this process and increasing toxic free heme levels[4][6][7]. HRP II is also used diagnostically as a marker in malaria rapid tests. Mislabeling this target as a "heme polymerase enzyme" is incorrect; current consensus identifies HRP II as the main molecular agent in hemozoin formation[7].

Other names

HRP IIHRP IIIHistidine-rich protein IIIHemozoin synthase (non-canonical, rarely used)Plasmodium falciparum hemozoin formation protein

Inhibition of hemozoin formation (drugs bind free heme or block its protein-mediated polymerization, causing toxic heme accumulation)