GLYCOLYTIC PATHWAY OF THE HUMAN MALARIA PARASITE PLASMODIUM-FALCIPARUM - PRIMARY SEQUENCE-ANALYSIS OF THE GENE ENCODING 3-PHOSPHOGLYCERATE KINASE AND CHROMOSOMAL MAPPING STUDIES

We have isolated and characterised the gene (PGK) encoding the glycolytic enzyme 3-phosphoglycerate kinase (PGK) from the human malaria parasite Plasmodium falciparum. This was achieved using the polymerase chain reaction (PCR) to amplify genomic DNA with primers constructed on the basis of conserved regions identified within PGK molecules of other organisms, and using the PCR product to isolate genomic clones. The gene is present in a single copy, encoding a protein of 416 amino acids (aa). The predicted aa sequence (45.5 kDa) displays approx. 60% identity to both human and yeast PGK molecules, and of the three P. falciparum glycolytic enzymes reported to date, has the greatest sequence identity to the host homologue. All aa residues implicated in substrate and cofactor binding and catalysis are conserved in the malarial PGK molecule, but there are major differences in overall composition, with implications for enzyme stability. In asexual blood-stage parasites, a single mRNA transcript of approx. 2.1 kb is observed. We have mapped the PGK gene to chromosome 9 of the parasite, and a further gene encoding a glycolytic enzyme, aldolase, to chromosome 14.