Malaria parasite-synthesized heme is essential in the mosquito and liver stages and complements host heme in the blood stages of infection

PLoS Pathog. 2013;9(8):e1003522. doi: 10.1371/journal.ppat.1003522. Epub 2013 Aug 1.


Heme metabolism is central to malaria parasite biology. The parasite acquires heme from host hemoglobin in the intraerythrocytic stages and stores it as hemozoin to prevent free heme toxicity. The parasite can also synthesize heme de novo, and all the enzymes in the pathway are characterized. To study the role of the dual heme sources in malaria parasite growth and development, we knocked out the first enzyme, δ-aminolevulinate synthase (ALAS), and the last enzyme, ferrochelatase (FC), in the heme-biosynthetic pathway of Plasmodium berghei (Pb). The wild-type and knockout (KO) parasites had similar intraerythrocytic growth patterns in mice. We carried out in vitro radiolabeling of heme in Pb-infected mouse reticulocytes and Plasmodium falciparum-infected human RBCs using [4-(14)C] aminolevulinic acid (ALA). We found that the parasites incorporated both host hemoglobin-heme and parasite-synthesized heme into hemozoin and mitochondrial cytochromes. The similar fates of the two heme sources suggest that they may serve as backup mechanisms to provide heme in the intraerythrocytic stages. Nevertheless, the de novo pathway is absolutely essential for parasite development in the mosquito and liver stages. PbKO parasites formed drastically reduced oocysts and did not form sporozoites in the salivary glands. Oocyst production in PbALASKO parasites recovered when mosquitoes received an ALA supplement. PbALASKO sporozoites could infect mice only when the mice received an ALA supplement. Our results indicate the potential for new therapeutic interventions targeting the heme-biosynthetic pathway in the parasite during the mosquito and liver stages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5-Aminolevulinate Synthetase / genetics
  • 5-Aminolevulinate Synthetase / metabolism*
  • Animals
  • Anopheles / parasitology*
  • Ferrochelatase / genetics
  • Ferrochelatase / metabolism*
  • Heme / biosynthesis*
  • Heme / genetics
  • Hemeproteins / biosynthesis
  • Hemeproteins / genetics
  • Humans
  • Liver / parasitology*
  • Liver / pathology
  • Malaria, Falciparum / enzymology*
  • Malaria, Falciparum / genetics
  • Mice
  • Oocysts / enzymology
  • Plasmodium berghei / enzymology*
  • Plasmodium berghei / genetics
  • Plasmodium falciparum / enzymology*
  • Plasmodium falciparum / genetics
  • Sporozoites / enzymology


  • Hemeproteins
  • hemozoin
  • Heme
  • 5-Aminolevulinate Synthetase
  • Ferrochelatase

Grants and funding

VAN is a DST Ramanujan Fellow. GP is an INSA Senior Scientist and supported by the NASI-PLATINUM JUBILEE CHAIR and Centre of Excellence Grant from the Department of Biotechnology, New Delhi. This study was supported by grants from the Department of Biotechnology (BT/01/10/MPB/DT) and Department of Science and Technology (SR/S2/RJN-13/2010), New Delhi. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.