Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dihydropteroate synthase (H2Pte synthase) is the target of the sulfur-based antimalarial drugs, which are frequently used in synergistic combination with inhibitors of dihydrofolate reductase (H2folate reductase) to combat chloroquine-resistant malaria. We have isolated the H2Pte synthase coding sequence of the most pathogenic human parasite Plasmodium falciparum. It forms part of a longer coding sequence, located on chromosome 8, that also specifies 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (CH2OH-H2pterinPP kinase) at its 5' proximal end. This domain is unusually large, with two long insertions relative to other CH2OH-H2pterinPP kinase molecules. To investigate a possible genetic basis for clinical resistance to sulfa drugs, we sequenced the complete H2Pte synthase domains from eleven isolates of P. falciparum with diverse geographical origins and levels of sulfadoxine resistance. Overall, point mutations in five positions were observed, affecting four codons. Parasite lines exhibiting high-level resistance were found to carry either a double mutation, altering both Ser436 and Ala613, or a single mutation affecting Ala581. The mutations at positions 436 and 581 have the same location relative to each of two degenerate repeated amino acid motifs that are conserved across all other known H2Pte synthase molecules. The amino acid alteration at residue 613 is identically positioned relative to a different conserved motif. The fourth amino acid residue (437) affected by mutation, though adjacent to the apparently crucial residue 436, shows no obvious correlation with resistance. Although these mutations have no exact counterparts in any other organism, that at position 581 falls within a region of three amino acids where H2Pte synthase is modified in various ways in a number of sulfonamide-resistant pathogenic bacteria. Copy-number analysis indicated that there was no amplification of the H2Pte synthase domain in resistant parasite lines of P. falciparum, compared to sensitive lines.
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PMID:Sequence variation of the hydroxymethyldihydropterin pyrophosphokinase: dihydropteroate synthase gene in lines of the human malaria parasite, Plasmodium falciparum, with differing resistance to sulfadoxine. 792 53

Dihydropteroate synthase (dhps) and dihydrofolate reductase (dhfr) alleles were typed in 67 Malaysian Plasmodium falciparum isolates. The isolates were collected from two geographically distinct locations: 51 from Sabah, Malaysian Borneo, where sulfadoxine/pyrimethamine (SDX/PYR) is used to treat uncomplicated malaria and 16 from Peninsular Malaysia where in vivo resistance to SDX/PYR has been reported. A total of seven dhps alleles were identified with no significant difference in allele frequency between the 2 populations. Two of the dhps alleles described here have not been previously reported. Four dhfr alleles were detected in 67 P. falciparum isolates. Eighty-seven percent of the isolates from the Peninsula, where clinical SDX/PYR failure has been reported, had dhfr alleles with triple point mutations while all of the isolates from Sabah had dhfr alleles with 2 or less point mutations. The difference in dhfr allele frequency between the two populations was highly significant. There was no correlation between in vitro PYR response and accumulation of dhfr point mutations.
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PMID:Short report: differences in dihydrofolate reductase but not dihydropteroate synthase alleles in Plasmodium falciparum isolates from geographically distinct areas in Malaysia. 1142 58

Dihydropteroate synthase (DHPS) can metabolise sulfa drugs into sulfa-dihydropteroate (sulfa-DHP), which inhibits cell growth through competition with dihydrofolate (DHF), possibly indicating dihydrofolate reductase (DHFR) as the target of sulfa-DHP. The effect of over-production of DHFR on sulfa-DHP resistance was examined in Saccharomyces cerevisiae using a strain that requires DHF for growth. This strain was transformed with a plasmid which encodes over-production of DHFR in the presence of CuSO4. Over-production led to resistance to sulfa-DHP suggesting that sulfa-DHP targets DHFR. Spontaneous mutants hyper-resistant to sulfa-DHP did not show any changes within DHFR.
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PMID:Over-production of dihydrofolate reductase leads to sulfa-dihydropteroate resistance in yeast. 1525 Dec 11

Dihydropteroate synthase (DHPS) gene mutations have raised concerns about emerging sulfonamide resistance in Pneumocystis jirovecii. DHPS and dihydrofolate reductase (DHFR) gene products were amplified in clinical specimens from South African patients. One of 53 DHPS genes sequenced contained the double mutation Thr55Ala Pro57Ser. DHFR gene mutations detected were Ala67Val and the new mutations Arg59Gly and C278T.
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PMID:Dihydropteroate synthase and novel dihydrofolate reductase gene mutations in strains of Pneumocystis jirovecii from South Africa. 1575 Jan 28

Sulpha drugs act as competitive inhibitors of p-amino benzoic acid, an intermediate in the de novo folate pathway. Dihydropteroate synthase condenses sulpha drugs into sulpha-dihydropteroate (sulpha-DHP), which competes with dihydrofolate, the dihydrofolate reductase (DHFR) substrate. This designates DHFR as a possible target of sulpha-DHP. We suggest here that Plasmodium vivax DHFR is indeed the in vivo target of sulpha drugs. The wild-type DHFR expressed in Saccharomyces cerevisiae leads to cell growth inhibition, while sensitivity to the drug is exacerbated in the mutants. Contrary to what is observed with sulphanilamide, methotrexate is less effective on P. vivax-DHFR mutants than on wild-type mutant.
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PMID:Plasmodium vivax dihydrofolate reductase as a target of sulpha drugs. 1648 26

The mechanistic basis for the resistance of Mycobacterium tuberculosis to para-aminosalicylic acid (PAS), an important agent in the treatment of multidrug-resistant tuberculosis, has yet to be fully defined. As a substrate analog of the folate precursor para-aminobenzoic acid, PAS is ultimately bioactivated to hydroxy dihydrofolate, which inhibits dihydrofolate reductase and disrupts the operation of folate-dependent metabolic pathways. As a result, the mutation of dihydrofolate synthase, an enzyme needed for the bioactivation of PAS, causes PAS resistance in M. tuberculosis strain H37Rv. Here, we demonstrate that various missense mutations within the coding sequence of the dihydropteroate (H2Pte) binding pocket of dihydrofolate synthase (FolC) confer PAS resistance in laboratory isolates of M. tuberculosis and Mycobacterium bovis. From a panel of 85 multidrug-resistant M. tuberculosis clinical isolates, 5 were found to harbor mutations in the folC gene within the H2Pte binding pocket, resulting in PAS resistance. While these alterations in the H2Pte binding pocket resulted in reduced dihydrofolate synthase activity, they also abolished the bioactivation of hydroxy dihydropteroate to hydroxy dihydrofolate. Consistent with this model for abolished bioactivation, the introduction of a wild-type copy of folC fully restored PAS susceptibility in folC mutant strains. Confirmation of this novel PAS resistance mechanism will be beneficial for the development of molecular method-based diagnostics for M. tuberculosis clinical isolates and for further defining the mode of action of this important tuberculosis drug.
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PMID:Binding pocket alterations in dihydrofolate synthase confer resistance to para-aminosalicylic acid in clinical isolates of Mycobacterium tuberculosis. 2436 31

Staphylococcal species are a leading cause of bacterial drug-resistant infections and associated mortality. One strategy to combat bacterial drug resistance is to revisit compromised targets, and to circumvent resistance mechanisms using structure-assisted drug discovery. The folate pathway is an ideal candidate for this approach. Antifolates target an essential metabolic pathway, and the necessary detailed structural information is now available for most enzymes in this pathway. Dihydropteroate synthase (DHPS) is the target of the sulfonamide class of drugs, and its well characterized mechanism facilitates detailed analyses of how drug resistance has evolved. Here, we surveyed clinical genetic sequencing data in S. aureus to distinguish natural amino acid variations in DHPS from those that are associated with sulfonamide resistance. Five mutations were identified, F17L, S18L, T51M, E208K, and KE257_dup. Their contribution to resistance and their cost to the catalytic properties of DHPS were evaluated using a combination of biochemical, biophysical and microbiological susceptibility studies. These studies show that F17L, S18L, and T51M directly lead to sulfonamide resistance while unexpectedly increasing susceptibility to trimethoprim, which targets the downstream enzyme dihydrofolate reductase. The secondary mutations E208K and KE257_dup restore trimethoprim susceptibility closer to wild-type levels while further increasing sulfonamide resistance. Structural studies reveal that these mutations appear to selectively disfavor the binding of the sulfonamides by sterically blocking an outer ring moiety that is not present in the substrate. This emphasizes that new inhibitors must be designed that strictly stay within the substrate volume in the context of the transition state.
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PMID:The Structural and Functional Basis for Recurring Sulfa Drug Resistance Mutations in Staphylococcus aureus Dihydropteroate Synthase. 3006 3