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Dual-Target Inhibitors of the Folate Pathway Inhibit Intrinsically Trimethoprim-Resistant DfrB Dihydrofolate
Jacynthe L Toulouse1,2,3, Genbin Shi4, Claudèle Lemay-St-Denis1,2,3
1Département de biochimie, Université de Montréal, Montréal, Quebec H3T 1J4, Canada.
New dihydrofolate reductases (DfrBs) confer trimethoprim resistance in microbes. Novel inhibitors targeting both DfrB and HPPK enzymes show promise for combating drug resistance.
Area of Science:
- Microbiology
- Biochemistry
- Drug Discovery
Background:
- Trimethoprim (TMP) resistance is increasing due to its widespread use in human and veterinary medicine.
- Plasmid-borne Type II dihydrofolate reductases (DfrBs) are a novel class of TMP-resistant enzymes, distinct from chromosomal Dfrs.
Purpose of the Study:
- To kinetically characterize DfrB enzymes and assess their susceptibility to TMP.
- To investigate the efficacy of bisubstrate inhibitors of 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) against DfrBs.
Main Methods:
- Kinetic characterization of DfrB enzyme family members.
- Assays to determine inhibition by TMP and novel HPPK inhibitors.
Main Results:
- DfrB enzymes exhibit conserved kinetic constants and are poorly inhibited by TMP, confirming intrinsic resistance.
- All DfrB family members were effectively inhibited by HPPK inhibitors.
Conclusions:
- DfrBs represent a significant mechanism of TMP resistance.
- Bisubstrate inhibitors of HPPK are effective dual-target inhibitors of microbial folate pathway enzymes, offering a potential strategy against TMP resistance.
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