Involvement of δ-aminolaevulinate synthase encoded by the parasite gene in de novo haem synthesis by Plasmodium falciparum

Abstract

The malaria parasite can synthesize haem de novo. In the present study, the expression of the parasite gene for delta-aminolaevulinate synthase (Pf ALAS ) has been studied by reverse transcriptase PCR analysis of the mRNA, protein expression using antibodies to the recombinant protein expressed in Escherichia coli and assay of ALAS enzyme activity in Plasmodium falciparum in culture. The gene is expressed through all stages of intra-erythrocytic parasite growth, with a small increase during the trophozoite stage. Antibodies to the erythrocyte ALAS do not cross-react with the parasite enzyme and vice versa. The recombinant enzyme activity is inhibited by ethanolamine and the latter inhibits haem synthesis in P. falciparum and growth in culture. The parasite ALAS is localized in the mitochondrion and its import into mitochondria in a cell-free import assay has been demonstrated. The import is blocked by haemin. On the basis of these results, the following conclusions are arrived at: PfALAS has distinct immunological identity and inhibitor specificity and is therefore a drug target. The malaria parasite synthesizes haem through the mitochondrion/cytosol partnership, and this assumes significance in light of the presence of apicoplasts in the parasite that may be capable of independent haem synthesis. The Pf ALAS gene is functional and vital for parasite haem synthesis and parasite survival.

The Plasmodium falciparum sexual development transcriptome: A microarray analysis using ontology-based pattern identification

“…Furthermore, evidence for the importance of organelle function during sexual development is provided by our data, as we showed significant up regulation of transcripts during gametocytogenesis for three of the six genes currently identified as part of the heme biosynthesis pathway in P. falciparum for which our microarray had probes. These included the mitochrondion-localized enzyme, ␦-aminolevulinate synthetase (1st step) [38,39], as well as the enzymes porphobilinogen deaminase (3rd step) and uroporphyrinogen decarboxylase (5th step), both thought to be localized to the apicoplast [39]. De novo heme biosynthesis may be important during the sexual stages as the parasite leaves the hemoglobin-rich blood environment of the human host.…”

Enzymes of the Heme Biosynthetic Pathway in the Nonphotosynthetic Alga Polytomella sp

“…In contrast, the malaria parasite, Plasmodium falciparum, even though possessing a plastid remnant, apparently does not contain a gene for GSAT. Instead, P. falciparum synthesizes ALA in the mitochondria via the ALA synthase route (44,53).…”

Distinct Prominent Roles for Enzymes of Plasmodium berghei Heme Biosynthesis in Sporozoite and Liver Stage Maturation

“…The potential advantage for compartmentalization of these three enzymes, which are typically cytoplasmic, remains enigmatic. All other enzymes in the pathway, such as the mitochondrial aminolevulinic acid synthase (ALAS), which catalyzes the first and rate-limiting step, display a standard subcellular distribution between mitochondrion and cytoplasm (13)(14)(15) (Fig. 1A).…”