Inhibition of dihydrofolate synthetase from Neisseria gonorrhoeae by dihydropteroate and dihydrofolate derivatives

Inhibitors of de novo folate enzymes in Plasmodium falciparum

Antifolates, inhibitors of folate synthesis or folate conversion, are used for malaria treatment. They are developed as synergistic combinations of inhibitors of dihydrofolate reductase (DHFR) and of dihydropteroate synthase (DHPS). DHPS inhibitors are sulfur-based drugs, analogs of sulfanilamide. These compounds compete with para-aminobenzoic acid in the active site of DHPS. The discovery of new antifolates is based on the identification of DHFR inhibitors; little work has been done on sulfur-based drugs because of their toxicity. As a result, only a few sulfur-based drugs are available. In this review, the hypothesis that compounds that compete with pteridine derivatives in active sites of de novo folate enzymes can be used as synergizers of DHFR inhibitors is discussed. If correct, this could lead to the identification of a new family of synergizers of DHFR inhibitors.

The folic acid biosynthesis pathway in bacteria: evaluation of potential for antibacterial drug discovery

The potential of the folic acid biosynthesis pathway as a target for the development of antibiotics has been acknowledged for many years and validated by the clinical use of several drugs. Recently, the crystal structures of all but one of the enzymes in the pathway from GTP to dihydrofolate have been determined. Given that structure-based drug design strategies are now widely employed, these recent developments have prompted a re-evaluation of the potential of each of the enzymes in the pathway as a target for development of specific inhibitors. Here, we review the current knowledge of the structure and mechanism of each enzyme in the bacterial folic acid biosynthesis pathway from GTP to dihydrofolate and draw conclusions regarding the potential of each enzyme as a target for therapeutic intervention.

Characterization and inhibition of dihydrofolate synthetase from Neisseria gonorrhoeae

Dihydrofolate synthetase (EC 6.3.2.12) from N. gonorrhoeae was isolated and enzyme characteristics were determined. The purified enzyme was found quite stable when stored at -60 degrees C. About 50% of the enzyme activity was destroyed within 6 weeks when kept at 4 degrees C. Maximum velocity was observed at pH 9.3. The enzyme required a monovalent cation, K+ or NH4+, and divalent cation, Mg2+ or Mn2+, for its function. ATP at 5 mM concentration gave maximum activity. Km values for dihydropteroate and L-glutamate at pH 9.3 were 3.5 X 10(-5) M and 6.5 X 10(-4) M, respectively. Patterns of product inhibition by dihydrofolate were found to be non-competitive with respect to dihydropteroate, having a Ki value of 5.1 +/- 0.8 X 10(-4) M, and competitive with respect to L-glutamate, having a Ki value of 6.2 X 10(-4) M.