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Malarial dihydroorotate dehydrogenase. Substrate and inhibitor specificity
Jeffrey Baldwin1, Azizeh M Farajallah, Nicholas A Malmquist
1Department of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, 75390-9041, USA.
The Journal of Biological Chemistry
|August 22, 2002
Summary
Malaria parasites synthesize pyrimidines using dihydroorotate dehydrogenase (DHODH). This study characterized the malarial DHODH, finding its active site differs from human DHODH, making it a promising target for new antimalarial drugs.
Area of Science:
- Biochemistry
- Parasitology
- Drug Discovery
Background:
- Malaria parasites depend on de novo pyrimidine biosynthesis, unlike human cells.
- Dihydroorotate dehydrogenase (DHODH) is a crucial enzyme in this pathway.
- Understanding malarial DHODH is key to developing targeted antimalarial therapies.
Purpose of the Study:
- To biochemically characterize Plasmodium falciparum DHODH.
- To investigate the substrate specificity and cofactor requirements of malarial DHODH.
- To assess the potential of malarial DHODH as a drug target by testing known mammalian DHODH inhibitors.
Main Methods:
- Expressed a truncated, soluble version of P. falciparum DHODH in E. coli.
- Determined enzyme kinetics, cofactor binding (FMN), and pH optimum.
- Tested various ubiquinone analogs and known mammalian DHODH inhibitors.
Main Results:
- Recombinant malarial DHODH exhibited optimal activity at pH 8.0 with efficient utilization of CoQ(4), CoQ(6), and decylubiquinone.
- Inhibitors of mammalian DHODH showed significantly lower efficacy against the malarial enzyme (100-10,000-fold higher IC50 values).
- This species-specific inhibition highlights differences in the active sites of malarial and human DHODH.
Conclusions:
- The malarial DHODH active site possesses distinct structural and functional properties compared to its human counterpart.
- These differences confirm malarial DHODH as a highly attractive and specific target for novel antimalarial drug development.
- Further research into malarial DHODH inhibitors could lead to effective treatments against malaria.