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)

With the aim of developing anticancer compounds which overcome some of the clinical limitations of the polar dihydrofolate reductase inhibitor, methotrexate, the physicochemical properties, kinetics, and metabolism of a series of lipid-soluble 2,4-diamino-5-phenylpyrimidine folate antagonists have been studied. Metoprine and etoprine, potent inhibitors of mammalian dihydrofolate reductase, were compared with pyrimethamine, a widely used antimalarial drug. The development of assay procedures in our laboratory and the synthesis of radiolabeled compounds have enabled a comparison of the kinetic characteristics and tissue distribution of these compounds in several species. The relative lipophilicities as indicated by the octanol/water partition coefficient are: etoprine (log P = 3.19) greater than metoprine (log P = 2.82) greater than pyrimethamine (log P = 2.69). Etoprine has the greatest affinity for plasma proteins, but all three compounds are bound to human plasma protein by 87% or more at therapeutic concentrations. Pharmacokinetic studies in the mouse, rat, dog, and man indicate that metoprine has the longest plasma half-life in all four species. The mean plasma half-lives in man are: pyrimethamine, 85 hr; metoprine, 216 hr; etoprine, 176 hr.
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PMID:Lipid-soluble inhibitors of dihydrofolate reductase. I. Kinetics, tissue distribution, and extent of metabolism of pyrimethamine, metoprine, and etoprine in the rat, dog, and man. 2 55

Floxacrine (HOE 991), 7-chloro-10-hydroxy-3-(4-trifluoromethylphenyl)3,4-dihydroacridine-1,9-(2H, 10H) dion, shows a high level of antimalarial action against blood-induced infection of drug-sensitive and drug-resistant lines of Plasmodium berghei in mice, rats and Syrian hamsters. The drug is also a potent blood schizontocide against drug-sensitive P. vinckei strains in rodents and P. cynomolgi in rhesus monkeys. The CD50/CD90 values against the drug-sensitive P. berghei strain ascertained in the '28-day test' in mice were 4.3/6.7 mg/kg after the oral route and 1.7/3.6 mg/kg after the subcutaneous (sc) route. In the 'two- and four-day test' the ED50 against sensitive P. vinckei was 0.7 mg/kg in both mice and rats. A moderate prophylactic effect could be demonstrated after the sc route probably due to a 'depot effect' of the water-insoluble active principle. Floxacrine was also highly active against P. berghei-lines which were resistant to chloroquine, mepacrine, dihydrofolate reductase inhibitors, sulfadoxine and dapsone. Resistance to HOE 991 could be developed in P. berghei and P. cynomolgi when the compound was used alone and administered repeatedly in subcurative doses. The antimalarial activity of the compound was not influenced by p-aminobenzoic acid or folic acid supplements in diets. Structural changes induced by floxacrine on pigment cytoplasm and nucleus in erythrocytic stages of P. berghei differed in some aspects from those of mepacrine and chloroquine. It is therefore assumed that the mode of action of floxacrine differs from that of the known antimalarial drugs. The general tolerance of the compound in rodents and rhesus monkeys is good and there is a wide range between the effective and maximum tolerated doses. Floxacrine was also effective at 100 ppm against pathogen Eimeria species in chickens, at 1000 mg/kg orally against Fasciola hepatica in rats and at 300-800 mg/kg orally against Heterakis spumosa in rats.
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PMID:Antimalarial activity of Floxacrine (HOE 991) I. Studies on blood schizontocidal action of Floxacrine against Plasmodium berghei, P. vinckei and P. cynomolgi. 12 Jan 42

A method for the high-voltage electrophoresis of dihydrofolate reductase from Escherichia coli W 3110 is described. Dihydrofolate reductase catalyses the reduction of dihydrofolic acid to tetrahydrofolic acid. By addition of a tetrazolium salt, tetrahydrofolic acid reacts by formation of a violet water insoluble formazane which is an indicator for the enzyme. Besides several unspecific bands, two isoenzymes of the dihydrofolate reductase from Escherichia coli W 3110 are found which are specificially inhibited by the folate antagonists methotrexate and trimethoprime in a concentration of 0, 1muM, 1 muM respectively.
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PMID:[High-voltage electrophoresis of dihydrofolate reductase from Escherichia coli W 3110 (author's transl)]. 32 Jun 38

The average number of infective larvae recovered from Brugia pahangi-infected Aedes aegypti was approximately one-half that recovered from the controls after the former group of infected mosquitoes had ingested a 1.0% solution of sulfisoxazole diolamine (SXZ) in 10% sucrose-water for 4 consecutive days, beginning 4 days after infection. Most of the filarial larvae from the SXZ-treated mosquitoes were small and sluggish compared with those from the controls. There was no increased mortality of mosquitoes that ingested 1.0% SXZ in sugar-water for 4 days. Average filarial larval burdens were not decreased in mosquitoes that ingested a solution of 10(-6) M methotrexate (MTX), a potent dihydrofolate reductase inhibitor, in sugar-water for 4 days, beginning 4 days after infection. The distributional pattern of larval burdens in mosquitoes that ingested combined 1.0% SXZ and 10(-6) M MTX in sugar-water for 4 days closely resembled that seen in mosquitoes that had imbibed 1.0% SXZ only. Average filarial larval burdens were not decreased in mosquitoes with 4-day-old B. pahangi infections that fed upon jirds which received intraperitoneal injections of SXZ (2 g/kg) and MTX (1 mh/kh), alone and in combination, 1 hr previously. Survival of the mosquitoes that fed upon the drug-treated hosts was unaffected, as was the hatchability of their eggs and subsequent growth and development of the mosquito larvae.
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PMID:Evidence that sulfisoxazole, an antibacterial sulfonamide, can adversely affect the development of Brugia pahangi in Aedes aegypti mosquitoes. 64 60

Pentamidine is an aromatic diamidino compound synthesized originally for the therapy of trypanosomiasis. The pharmacologic effects of pentamidine vary, depending on its route of administration. In animals, the dominant effects have been a precipitous, transitory drop in blood pressure after injection and renal toxicity following repeated administration. To avoid the possibility of immediate toxic reactions associated with iv administration, we now usually give the drug im to humans. Further interest in pentamidine has been stimulated by its usefulness in the treatment of interstitial pneumonia caused by Pneumocystis carinii. In some patients receiving antineoplastic or immunosuppressive therapy who have superimposed P. carinii pneumonia, pentamidine may cause serious renal toxicity. Distribution and excretion studies in animals indicate pentamidine is deposited in tissues, with the greatest concentration in the kidneys, and gradually eliminated over a prolonged period. The mechanism of action of pentamidine against P. carinii or the means whereby fixation in tissues and subsequent toxicity occur have not been elucidated. Recent investigations to help clarify these points indicate that pentamidine inhibits dihydrofolate reductase in all tissues studied both in vitro and in vivo. In addition, pentamidine interacts and forms water-insoluble products with specific nucleotides and nucleic acids.
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PMID:Pharmacologic aspects of pentamidine. 101 18

The crystal structure of the methotrexate-gamma-tetrazole (MTXT)-NADPH ternary complex with recombinant human dihydrofolate reductase (DHFR) has been determined and refined to R = 15.9% for 7003 data from 10.0 to 2.3 A resolution for the R3 lattice. Interpretation of difference Fourier electron density maps revealed that the cofactor NADPH is bound in an extended conformation, and the closest contact between cofactor and inhibitor is 3.1 A, between N(5) of the MTXT pteridine ring and the nicotinamide C(4) which transfers a hydride during the enzyme-catalyzed reaction. As in other DHFR complexes, MTXT is interpreted as protonated at N(1) by Glu-30, and the 2-amino group is hydrogen bonded to a structurally conserved water which also interacts with Glu-30 and Thr-136. The 4-amino group of MTXT hydrogen bonds to the carbonyl of Ile-7 and the phenolic hydroxyl of Tyr-121, and the alpha-carboxylate forms a salt bridge with the conserved Arg-70. In this structure, the amide carbonyl forms two hydrogen bonds with Asn-64 and a water molecule, whereas the gamma-tetrazole ring does not interact directly with the enzyme. The largest changes in the secondary structure on formation of the ternary complex involve the fold of a flexible loop near residues 40-46, and to a lesser extent the helical region near residues 102-109 and the beta-sheet regions near residues 71-75 and 157-159.
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PMID:Crystal structure determination at 2.3 A of recombinant human dihydrofolate reductase ternary complex with NADPH and methotrexate-gamma-tetrazole. 128 40

The 2.2-A crystal structure of chicken liver dihydrofolate reductase (EC 1.5.1.3, DHFR) has been solved as a ternary complex with NADP+ and biopterin (a poor substrate). The space group and unit cell are isomorphous with the previously reported structure of chicken liver DHFR complexed with NADPH and phenyltriazine [Volz, K. W., Matthews, D. A., Alden, R. A., Freer, S. T., Hansch, C., Kaufman, B. T., & Kraut, J. (1982) J. Biol. Chem. 257, 2528-2536]. The structure contains an ordered water molecule hydrogen-bonded to both hydroxyls of the biopterin dihydroxypropyl group as well as to O4 and N5 of the biopterin pteridine ring. This water molecule, not observed in previously determined DHFR structures, is positioned to complete a proposed route for proton transfer from the side-chain carboxylate of E30 to N5 of the pteridine ring. Protonation of N5 is believed to occur during the reduction of dihydropteridine substrates. The positions of the NADP+ nicotinamide and biopterin pteridine rings are quite similar to the nicotinamide and pteridine ring positions in the Escherichia coli DHFR.NADP+.folate complex [Bystroff, C., Oatley, S. J., & Kraut, J. (1990) Biochemistry 29, 3263-3277], suggesting that the reduction of biopterin and the reduction of folate occur via similar mechanisms, that the binding geometry of the nicotinamide and pteridine rings is conserved between DHFR species, and that the p-aminobenzoylglutamate moiety of folate is not required for correct positioning of the pteridine ring in ground-state ternary complexes. Instead, binding of the p-aminobenzoylglutamate moiety of folate may induce the side chain of residue 31 (tyrosine or phenylalanine) in vertebrate DHFRs to adopt a conformation in which the opening to the pteridine binding site is too narrow to allow the substrate to diffuse away rapidly. A reverse conformational change of residue 31 is proposed to be required for tetrahydrofolate release.
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PMID:Crystal structure of chicken liver dihydrofolate reductase complexed with NADP+ and biopterin. 151 Sep 19

Proton nuclear magnetic resonance spectroscopy has been used to detect two water molecules bound to residues in the active site of the Lactobacillus casei dihydrofolate reductase (DHFR). Their presence was detected by measuring nuclear Overhauser effects between NH protons in protein residues and protons in the individual bound water molecules in two-dimensional nuclear Overhauser effect spectroscopy (NOESY), in nuclear Overhauser effect spectroscopy in the rotating frame (ROESY) and three-dimensional 1H-15N ROESY-heteronuclear multiple quantum coherence spectra recorded on samples containing appropriately 15N-labelled DHFR. For the DHFR-methotrexate-NADPH complex, two bound molecules were found, one close to the Trp5 amide NH proton and the other near to the Trp21 indole HE1 proton: these correspond to two of the water molecules (Wat201 and Wat253) detected in the crystal structure studies described by Bolin and co-workers. However, the nuclear magnetic resonance experiments did not detect any of the other bound water molecules observed in the X-ray studies. The nuclear magnetic resonance results indicate that the two bound water molecules that were detected have lifetimes in the solution state that are longer than approximately two nanoseconds. This is of considerable interest, since one of these water molecules (Wat253) has been implicated as the likely proton donor in the catalytic reduction of dihydrofolate to tetrahydrofolate.
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PMID:Nuclear magnetic resonance detection of bound water molecules in the active site of Lactobacillus casei dihydrofolate reductase in aqueous solution. 164 Apr 65

Pneumocystis carinii is known to proliferate mainly in the lung of an immunocompromised host. In AIDS and other immune disorders sporadic extrapulmonary presence of this organism has been documented. Occasionally, P. carinii does not appear to infect the lung. These observations have been based on the detection of P. carinii by conventional staining techniques. We have sought to determine the extent of these infections by the polymerase chain reaction (PCR) in a rat model. Harlan Sprague-Dawley rats weighing between 110 and 130 g were immunosuppressed with dexamethasone (1.2 mg/l) in drinking water. During progressive stages of immunosuppression 2 rats were sacrificed at 2, 3, 4 and 5 wk, and the lung, liver, kidney, spleen and bone marrow were taken. Sonicated crude extracts of the tissues were used as template DNA for the amplification of the dihydrofolate reductase (DHFR) gene of P. carinii. All the PCR products were analyzed by Southern hybridization with radiolabelled DHFR DNA. These analyses revealed a general trend of P. carinii proliferation first in bone marrow at 2 wk, followed by liver at 3 wk, and lung at 5 wk on immunosuppression. Kidney and spleen infections were infrequent. Although P. carinii appears to proliferate in the lung at later stages of immunosuppression, the degree of proliferation is several-fold greater than in extrapulmonary organs. The extrapulmonary proliferation of P. carinii, however small, may possibly suppress hematopoietic stem cell differentiation in bone marrow, and may also contribute to the pathology present in various organs.
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PMID:Proliferation patterns of latent Pneumocystis carinii in rat organs during progressive stages of immunosuppression. 152 78

The importance of three amino acid residues contacting the nicotinamide ring of NADPH in Escherichia coli dihydrofolate reductase has been defined using site-directed mutagenesis and detailed steady-state and pre-steady-state kinetic experiments. Replacement of Tyr-100 with either glycine or isoleucine (Y100G or Y100I) disrupts an aromatic-aromatic interaction between the phenolic side chain and the nicotinamide ring. Both mutations remove the differential binding of the oxidized and reduced coenzymes implicating Tyr-100 as a major determinant for coenzyme specificity. Replacement of Ser-49 for alanine (S49A), designed to either displace or reduce the polarizability of a bound water molecule contacting the N1 of the nicotinamide ring, affects only the rate of release of NADP+. Replacement of Ile-14 with alanine (I14A), designed to alter both a weakly polar and a hydrogen bonding interaction with the periphery of the nicotinamide ring, affects only the binding of NADPH. Y100I, Y100G, and I14A all increase the activation barrier for the chemical step by approximately 2 kcal/mol. The lack of an effect for S49A suggests that water structure is not important for stabilizing the hydride transfer transition state. In addition, the nominal effects observed for these mutations disfavor the hypothesis that neighboring amino acid residues participate in the stabilization of the reaction transition state through polar or weakly polar contacts.
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PMID:The function of amino acid residues contacting the nicotinamide ring of NADPH in dihydrofolate reductase from Escherichia coli. 183 73


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