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What is the function of dihydrofolate reductase?
Dihydrofolate reductase (DHFR) catalyzes the reduction of dihydrofolate to tetrahydrofolate (THF). THF is needed for the action of folate-dependent enzymes and is thus essential for DNA synthesis and methylation.
Do bacteria have dihydrofolate reductase?
The enzyme dihydrofolate reductase (DHFR) occurs in all organisms and has been particularly well-studied in the bacterium Escherichia coli and in humans. It catalyzes the reduction of dihydrofolate to tetrahydrofolate, with NADPH acting as hydride donor.
Why is dihydrofolate reductase a drug target?
DHFR: the target Traditionally, several DHFR inhibitors are reported as potential drug candidates in various diseases. Folate metabolism has long been recognized as an important and attractive target for chemotherapy because of its crucial role in the biosynthesis of nucleic-acid precursors.
What happens when dihydrofolate reductase is inhibited?
The synthesis of folates in both eukaryotic and prokaryotic cells is strictly dependent on the activities of two enzymes: DHFR and dihydrofolate synthase (DHFS), whose inhibition leads to cell death.
Where is dihydrofolate reductase found?
It is found in the q11→q22 region of chromosome 5. Bacterial species possess distinct DHFR enzymes (based on their pattern of binding diaminoheterocyclic molecules), but mammalian DHFRs are highly similar.
Is dihydrofolate an enzyme?
Dihydrofolate reductase is a small enzyme that plays a supporting role, but an essential role, in the building of DNA and other processes. It manages the state of folate, a snaky organic molecule that shuttles carbon atoms to enzymes that need them in their reactions.
What inhibits bacterial dihydrofolate reductase?
Trimethoprim (TMP), (2,4-diamino-5-(3′,4′,5′-trimethoxybenzyl)pyrimidine) is the well-known dihydrofolate reductase inhibitor and one of the standard antibiotics used in urinary tract infections (UTIs).
How does TMP inhibit DHFR?
This antibiotic is a pyrimidine antifolate drug, which selectively inhibits the bacterial enzyme dihydrofolate reductase (DHFR). The mechanism of this inhibition consists in preventing the conversion of DHF to an active form, i.e., THF [3,32].
Which drug inhibits dihydrofolate reductase and the subsequent production of purines?
Methotrexate, the most commonly used and the most widely studied dihydrofolate reductase inhibitor is an effective therapeutics agent available to treat many solid tumors and autoimmune diseases such as rheumatoid arthritis. Other approved folate antagonists are pemetrexed (28.1. 41) and pralatrexate (28.1. 42).
Which of the following drug inhibit the dihydrofolate reductase enzyme?
Methotrexate. Methotrexate is a dihydrofolate reductase inhibitor that is used in the treatment of autoimmune inflammatory diseases such as RA.
Does methotrexate inhibit bacterial DHFR?
Methotrexate (MTX) is a folate analogue that inhibits the activity of dihydrofolate reductase (DHFR) (16), which catalyzes the NADPH-dependent reduction of dihydrofolate to tetrahydrofolate.
What is the mechanism of methotrexate?
Methotrexate inhibits dihydrofolate reductase, preventing the reduction of dihydrobiopterin (BH2) to tetrahydrobiopterin (BH4), leading to nitric oxide synthase uncoupling and increased sensitivity of T cells to apoptosis, thereby diminishing immune responses.
Does methotrexate inhibit bacterial DHFR?
Methotrexate (MTX) is a folate analogue that inhibits the activity of dihydrofolate reductase (DHFR) (16), which catalyzes the NADPH-dependent reduction of dihydrofolate to tetrahydrofolate.
Which of the following blocks the enzyme dihydrofolate reductase?
Sulfadoxine-Pyrimethamine Pyrimethamine inhibits parasite DHFR activity and the production of tetrahydrofolate, an essential cofactor for one-carbon metabolism required for the synthesis of nucleic acids and certain amino acids.
Which drug is act as folate reductase inhibitors?
Methotrexate. Methotrexate is a dihydrofolate reductase inhibitor that is used in the treatment of autoimmune inflammatory diseases such as RA.
How does trimethoprim inhibit dihydrofolate reductase?
Trimethoprim is 50,000 to 100,000 times more active against bacterial dihydrofolate reductase than against the human enzyme. Trimethoprim interferes with the conversion of dihydrofolate to tetrahydrofolate, the precursor of folinic acid and ultimately of purine and DNA synthesis (Fig. 33-3).
What is the function of dihydrofolate reductase?
Dihydrofolate reductase converts dihydrofolate into tetrahydrofolate, a proton shuttle required for the de novo synthesis of purines, thymidylic acid, and certain amino acids. While the functional dihydrofolate reductase gene has been mapped to chromosome 5, multiple intronless processed pseudogenes or dihydrofolate reductase-like genes have been identified on separate chromosomes.
What is the enzyme that converts dihydrofolic acid to tetrahydrofolic acid?
View/Edit Mouse. Dihydrofolate reductase, or DHFR, is an enzyme that reduces dihydrofolic acid to tetrahydrofolic acid, using NADPH as electron donor, which can be converted to the kinds of tetrahydrofolate cofactors used in 1-carbon transfer chemistry. In humans, the DHFR enzyme is encoded by the DHFR gene.
What are the classes of compounds that target DHFR?
Other classes of compounds that target DHFR in general, and bacterial DHFRs in particular, belong to the classes such as diaminopteridines, diaminotriazines, diaminopyrroloquinazolines, stilbenes, chalcones, deoxybenzoins, to name but a few.
What is the first step in the catalytic reaction?
Specifically, the catalytic reaction begins with the NADPH and the substrate attaching to the binding site of the enzyme, followed by the protonation and the hydride transfer from the cofactor NADPH to the substrate. However, two latter steps do not take place simultaneously in a same transition state.
What is DHFR in a cell?
DHFR plays a central role in the synthesis of nucleic acid precursors, and it has been shown that mutant cells that completely lack DHFR require glycine, an amino acid, and thymidine to grow. DHFR has also been demonstrated as an enzyme involved in the salvage of tetrahydrobiopterin from dihydrobiopterin.
What is the role of DHFR in cell growth?
Found in all organisms, DHFR has a critical role in regulating the amount of tetrahydrofolate in the cell. Tetrahydrofolate and its derivatives are essential for purine and thymidylate synthesis, which are important for cell proliferation and cell growth.
What is the main feature of the polypeptide backbone folding of DHFR?
A central eight-stranded beta-pleated sheet makes up the main feature of the polypeptide backbone folding of DHFR. Seven of these strands are parallel and the eighth runs antiparallel. Four alpha helices connect successive beta strands. Residues 9 – 24 are termed "Met20" or "loop 1" and, along with other loops, are part of the major subdomain that surround the active site. The active site is situated in the N-terminal half of the sequence, which includes a conserved Pro - Trp dipeptide; the tryptophan has been shown to be involved in the binding of substrate by the enzyme.
What is the name of the enzyme that converts dihydrofolate to tetrahydrofolic?
Dihydrofolate reductase (DHFR) is an enzyme which uses the co-factor NADPH as electron donor which converts it to NADP. It catalyzes the reduction of dihydrofolic acid to tetrahydrofolic acid (folate). The folate is a form of the essential vitamin B9. Trimethoprim (TMP) is a known inhibitor of DHFR. DHFR forms a complex with thymidylate synthase (TS). Both enzymes participate in the biosynthesis of pyrimidine. For more details see
What is the role of DHFR?
The primary physiological role of DHFR is maintenance of the intracellular levels of tetrahydrofolate, a precursor of cofactors required for the biosynthesis of purines, pyrimidines, and several amino acids.
What is DHFR inhibitor?
Thus far, all of the clinically useful drugs of this class have been inhibitors of dihydrofolate reductase (DHFR), a key enzyme in the synth …. The folate antagonists are an important class of therapeutic compounds, as evidenced by their use as antiinfective, antineoplastic, and antiinflammatory drugs. Thus far, all of the clinically useful drugs ...
What is folate antagonist?
The folate antagonists are an important class of therapeutic compounds, as evidenced by their use as antiinfective, antineoplastic, and antiinflammatory drugs. Thus far, all of the clinically useful drugs of this class have been inhibitors of dihydrofolate reductase (DHFR), a key enzyme in the synthesis of thymidylate, and therefore, of DNA.
Is methotrexate a species selective agent?
These species-selective agents apparently exploit the differences in the active site regions of the parasite and host enzymes. Methotrexate is the DHFR inhibitor used most often in a clinical setting as an anticancer drug and as an antiinflammatory and immunosuppressive agent.
Is dihydrofolate reductase a therapeutic target?
Dihydrofolate reductase as a therapeutic target. The folate antagonists are an important class of therapeutic compounds, as evidenced by their use as antiinfective, antineoplastic, and antiinflammatory drugs.
What is a dihydrofolate reductase inhibitor?
A dihydrofolate reductase inhibitor ( DHFR inhibitor) is a molecule that inhibits the function of dihydrofolate reductase, and is a type of antifolate . Since folate is needed by rapidly dividing cells to make thymine, this effect may be used to therapeutic advantage.
What inhibitors are used in the tetrahydrofolate synthesis pathway?
Tetrahydrofolate synthesis pathway. Classes of small-molecules employed as inhibitors of dihydrofolate reduc tase include diaminoquinazoline and diaminopyrroloquinazoline, Most of the above specified inhibitors are structural analogues of the substrate dihydrofolate and bind to the active site of the enzyme. Further, it has been recently shown that, ...
Why is methotrexate used in cancer?
For example, methotrexate is used as cancer chemotherapy because it can prevent neoplastic cells from dividing.
Do bacteria need DHFR?
Bacteria also need DHFR to grow and multiply and hence inhibitors selective for bacterial vs. host DHFR have found application as antibacterial agents. An extensive review of the chemical space of small-molecules that inhibit DHFR is summarized in.
Overview
Dihydrofolate reductase, or DHFR, is an enzyme that reduces dihydrofolic acid to tetrahydrofolic acid, using NADPH as electron donor, which can be converted to the kinds of tetrahydrofolate cofactors used in 1-carbon transfer chemistry. In humans, the DHFR enzyme is encoded by the DHFR gene. It is found in the q11→q22 region of chromosome 5. Bacterial species possess distinct DHFR en…
Structure
A central eight-stranded beta-pleated sheet makes up the main feature of the polypeptide backbone folding of DHFR. Seven of these strands are parallel and the eighth runs antiparallel. Four alpha helices connect successive beta strands. Residues 9 – 24 are termed "Met20" or "loop 1" and, along with other loops, are part of the major subdomain that surround the active site. The active site is situated in the N-terminal half of the sequence, which includes a conserved Pro-Trp dipepti…
Function
Dihydrofolate reductase converts dihydrofolate into tetrahydrofolate, a proton shuttle required for the de novo synthesis of purines, thymidylic acid, and certain amino acids. While the functional dihydrofolate reductase gene has been mapped to chromosome 5, multiple intronless processed pseudogenes or dihydrofolate reductase-like genes have been identified on separate chromoso…
Mechanism
DHFR catalyzes the transfer of a hydride from NADPH to dihydrofolate with an accompanying protonation to produce tetrahydrofolate. In the end, dihydrofolate is reduced to tetrahydrofolate and NADPH is oxidized to NADP+. The high flexibility of Met20 and other loops near the active site play a role in promoting the release of the product, tetrahydrofolate. In particular the Met20 loop helps …
Clinical significance
Dihydrofolate reductase deficiency has been linked to megaloblastic anemia. Treatment is with reduced forms of folic acid. Because tetrahydrofolate, the product of this reaction, is the active form of folate in humans, inhibition of DHFR can cause functional folate deficiency. DHFR is an attractive pharmaceutical target for inhibition due to its pivotal role in DNA precursor synthesis. Trimethoprim, an antibiotic, inhibits bacterial DHFR while methotrexate, a chemotherapy agent, in…
Therapeutic applications
Since folate is needed by rapidly dividing cells to make thymine, this effect may be used to therapeutic advantage.
DHFR can be targeted in the treatment of cancer and as a potential target against bacterial infections. DHFR is responsible for the levels of tetrahydrofolate in a cell, and the inhibition of DHFR can limit the growth and p…
As a research tool
DHFR has been used as a tool to detect protein–protein interactions in a protein-fragment complementation assay (PCA).
DHFR lacking CHO cells are the most commonly used cell line for the production of recombinant proteins. These cells are transfected with a plasmid carrying the dhfr gene and the gene for the recombinant protein in a single expression system, and then subjected to selective conditions in t…
Interactions
Dihydrofolate reductase has been shown to interact with GroEL and Mdm2.