Heme Detoxification Protein (HDP) (HDP)

The Heme Detoxification Protein (HDP), encoded by gene PF14_0446 in Plasmodium falciparum, is a 205-amino-acid polypeptide essential for converting toxic free heme—released from host hemoglobin degradation during the parasite's intraerythrocytic stages—into inert hemozoin crystals within the food vacuole. This process is critical for parasite survival, as free heme is highly toxic, and HDP demonstrates potent enzymatic activity, converting up to 50% of heme to hemozoin rapidly under acidic conditions (pH 5.2 or lower) mimicking the food vacuole milieu, with a conversion rate of 1566 heme molecules per HDP molecule per hour. HDP follows a unique "outbound-inbound" trafficking route: it is secreted from early ring-stage trophozoites into the infected red blood cell cytosol, then endocytosed via cytostomes along with hemoglobin into transport vesicles, and delivered to the food vacuole where hemozoin forms. The gene is single-copy, conserved across Plasmodium species, and cannot be disrupted, underscoring its essential role in sustaining parasite proliferation. In malaria, HDP enables unchecked hemoglobin digestion (up to 75% of red blood cell content), fueling parasite growth while averting heme-induced damage; its involvement positions it as a promising antimalarial drug target, though no specific inhibitors are clinically approved, unlike broader heme detoxification inhibitors like chloroquine or artemisinins that indirectly disrupt hemozoin formation. Native HDP functions as a dimer and is active in parasite extracts, distinguishing it from debated lipid- or autocatalytic mechanisms.

Other names

Plasmodium Heme Detoxification ProteinPF14_0446NP_702335