Title: Altered dihydrofolate reductase in pyrimethamine-resistant Plasmodium falciparum
Abstract: Dihydrofolate reductase (EC 1.5.1.3, tetrahydrofolate dehydrogenase), the target enzyme for the chemotherapeutic attack by pyrimethamine, has been studied in drug-sensitive and resistant strains of Plasmodium falciparum. No evidence was found for overproduction of this enzyme in drug-resistant strains. Results presented here indicate that pyrimethamine resistance of P. falciparum depends on a modified dihydrofolate reductase, which shows less affinity for pyrimethamine and dihydrofolate. The inhibition constants for pyrimethamine increased from 0.19 nM for the drug-sensitive strain FCH-5 to 4.1 and 21.6 nM for the drug-resistant strains FVOR and K 1, respectively. In addition, the Km-values for dihydrofolate increased from 2.5 μM to 21 and 28 μM, respectively. The type of inhibition by pyrimethamine changed from competitive with respect to dihydrofolate in drug-sensitive strain to non-competitive in drug-resistant strains of P. falciparum.
Publication Year: 1986
Publication Date: 1986-04-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 34
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