A bifunctional dihydrofolate synthetase--folylpolyglutamate synthetase in Plasmodium falciparum identified by functional complementation in yeast and bacteria

Mol Biochem Parasitol. 2001 Feb;112(2):239-52. doi: 10.1016/s0166-6851(00)00370-4.


Folate metabolism in the human malaria parasite Plasmodium falciparum is an essential activity for cell growth and replication, and the target of an important class of therapeutic agents in widespread use. However, resistance to antifolate drugs is a major health problem in the developing world. To date, only two activities in this complex pathway have been targeted by antimalarials. To more fully understand the mechanisms of antifolate resistance and to identify promising targets for new chemotherapies, we have cloned genes encoding as yet uncharacterised enzymes in this pathway. By means of complementation experiments using 1-carbon metabolism mutants of both Escherichia coli and Saccharomyces cerevisiae, we demonstrate here that one of these parasite genes encodes both dihydrofolate synthetase (DHFS) and folylpolyglutamate synthetase (FPGS) activities, which catalyse the synthesis and polyglutamation of folate derivatives, respectively. The malaria parasite is the first known example of a eukaryote encoding both DHFS and FPGS activities in a single gene. DNA sequencing of this gene in antifolate-resistant strains of P. falciparum, as well as drug-inhibition assays performed on yeast and bacteria expressing PfDHFS--FPGS, indicate that current antifolate regimes do not target this enzyme. As PfDHFS--FPGS harbours two activities critical to folate metabolism, one of which has no human counterpart, this gene product offers a novel chemotherapeutic target with the potential to deliver a powerful blockage to parasite growth.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cloning, Molecular
  • Escherichia coli / enzymology
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism
  • Folic Acid Antagonists / pharmacology
  • Gene Deletion
  • Genes, Protozoan / genetics
  • Genetic Complementation Test
  • Glycine / metabolism
  • Methionine / metabolism
  • Molecular Sequence Data
  • Multienzyme Complexes / chemistry
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism*
  • Peptide Synthases / chemistry
  • Peptide Synthases / genetics
  • Peptide Synthases / metabolism*
  • Plasmodium falciparum / enzymology*
  • Plasmodium falciparum / genetics
  • RNA, Fungal / analysis
  • RNA, Fungal / genetics
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism
  • Sequence Alignment
  • Transformation, Genetic


  • Folic Acid Antagonists
  • Multienzyme Complexes
  • RNA, Fungal
  • Methionine
  • Peptide Synthases
  • dihydrofolate synthetase
  • folylpolyglutamate synthetase
  • Glycine

Associated data

  • GENBANK/AF161264