Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Dihydropteridine Reductase”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1985

The enzymatic activities of GTP cyclohydrolase, sepiapterin reductase, dihydropteridine reductase and dihydrofolate reductase; and tetrahydrobiopterin content in mammalian ocular tissues and in human senile cataracts.

The enzymatic activities of GTP cyclohydrolase, sepiapterin reductase, dihydropterin reductase and dihydrofolate reductase were determined in the ocular tissues of rat, rabbit, calf and human. The enzymatic activities of the pteridine biosynthesis and the content of tetrahydropteridine (BH4) were higher in retina and ciliary body-iris as compared with lens tissue in all mammalian species tested. The activities of the pteridine synthesizing enzymes and BH4 content were decreased in human senile cataracts as compared with age-matched clear human lenses. The loss of BH4 may result in lenticular proteins more susceptible to oxidation and contribute to high molecular weight protein formation in cataracts.

Alcohol Oxidoreductases↗
PubMed2000

Molecular characterization of Drosophila melanogaster dihydropteridine reductase.

Dihydropteridine reductase (DHPR) catalyzes the NAD(P)H-mediated reduction of quinonoid dihydropteridine as a part of pterin-dependent aromatic amino acid hydroxylation. We isolated a fragment of Drosophila DHPR gene by PCR using degenerate primers. By screening a cDNA library, we obtained full-length clones. The predicted amino acid sequence of the Drosophila DHPR protein was highly homologous to other species including human and mouse. In particular, the Tyr-(Xaa)(3)-Lys motif, known as the NAD(P)H binding domain, and most amino acids relevant to quinonoid dihydropteridine binding site are identical to human DHPR. The recombinant DHPR protein expressed in Escherichia coli showed DHPR enzyme activity. Northern blot analysis revealed two transcripts of 1.1 and 0.9 kb. Genomic DNA sequencing revealed that the gene consists of two exons interrupted by a single 96-bp intron. The two transcripts have alternative promoters, both having no putative TATA box or CAAT box, but sharing a common poly(A)(+) signal. The existence of two alternative promoters suggests that each transcript be regulated independently through different stimuli. Further study is needed to examine the expression and function of the two alternative transcripts.

Amino Acid Sequence↗
PubMed1991

Inhibition of dopamine autoxidation by tetrahydrobiopterin and NADH in the presence of dihydropteridine reductase.

Dihydropteridine reductase (DHPR) catalyzes the regeneration of tetrahydrobiopterin (BH4) from quinonoid dihydrobiopterin by using NADH as a hydrogen donor. This enzymatic reaction has been found to serve as an antioxidation system during dopamine autoxidation in oxygenated Dulbecco's phosphate buffered saline (pH 7.5) at 37 degrees C. BH4 or NADH by itself has little or no inhibitory effect on dopamine autoxidation. The presence of DHPR, in addition to BH4 and NADH, greatly prolongs the lag period, which increases with increasing concentrations of each of BH4, NADH and DHPR. This BH4/DHPR-mediated antioxidation system is as effective as other antioxidation agents such as ascorbic acid, cysteine and reduced glutathione. Since BH4, NADH and DHPR are ubiquitous in mammalian tissues, this system may play an important role in the reduction of the oxidation products of catecholamines.

Animals↗
PubMed1987

Structure and expression of human dihydropteridine reductase.

Dihydropteridine reductase (DHPR; EC 1.6.99.7) catalyzes the NADH-mediated reduction of quinonoid dihydrobiopterin and is an essential component of the pterin-dependent aromatic amino acid hydroxylating systems. A cDNA for human DHPR was isolated from a human liver cDNA library in the vector lambda gt11 using a monospecific antibody against sheep DHPR. The nucleic acid sequence and amino acid sequence of human DHPR were determined from a full-length clone. A 112 amino acid sequence of sheep DHPR was obtained by sequencing purified sheep DHPR. This sequence is highly homologous to the predicted amino acid sequence of the human protein. Gene transfer of the recombinant human DHPR into COS cells leads to expression of DHPR enzymatic activity. These results indicate that the cDNA clone identified by antibody screening is an authentic and full-length cDNA for human DHPR.

Amino Acid Sequence↗
PubMed1989

Anti-idiotypic antibodies elicited by pterin recognize active site epitopes in dihydrofolate reductases and dihydropteridine reductase.

Monoclonal antibodies (mAbs) against antipterin immunoglobulin and dihydropteridine reductase (DHPR) and also polyclonal antibodies against human dihydrofolate reductase (DHFR) were obtained. The anti-idiotypic mAbs and anti-DHPR mAbs bind specifically to human DHFR, Escherichia coli DHFR, soybean seedling DHFR, and human DHPR in solid-phase immunoassays. Further, the mAbs bind to the native but not to the denatured forms of DHFRs. The monoclonal antibodies also inhibit the enzymatic activity of human DHFR but not that of human DHPR. Competitive solid-phase immunoassays show stoichiometric inhibition by methotrexate and partial inhibition by NADPH of mAb binding to human DHFR. Cyanogen bromide fragments derived from human DHFR (residues 15-52 and 53-111), containing several active site residues, bind partially to some of the monoclonal antibodies. Accordingly, polyclonal antibodies to peptide 53-111 of human DHFR cross-react to some extent with human DHPR. Data from competitive immunoassays in which the binding of the various mAbs was tested singly and in combination with other mAbs suggest that these antibodies bind to a common region on human DHFR. The results also indicate that the mAbs display some heterogeneity with respect to specific epitopes. These data suggest that despite the absence of significant amino acid sequence homologies among the various DHFRs and DHPR, they have a fundamentally similar topography at the site of binding of the pterin moiety that is recognized by the anti-idiotypic mAbs generated by pterin. In the relatively simple structure of the pterin ring system there are different substituent groups at positions C4 and C6 in methotrexate, 7,8-dihydrofolate, and 7,8-dihydrobiopterin, suggesting that these antibodies are specific for regions on various proteins that interact with the remainder of the pterin moiety. These mAbs and similar mAbs specified by substituent groups on pterin may thus be used as specific probes or inhibitors of various folate-dependent enzymes and transport proteins. They should also provide insights into some of the general features of antibody recognition of protein antigens.

Antibodies, Anti-Idiotypic↗
PubMed1987

Human dihydropteridine reductase: characterisation of a cDNA clone and its use in analysis of patients with dihydropteridine reductase deficiency.

Deficiency of human dihydropteridine reductase (hDHPR) causes malignant hyperphenylalaninemia. We report the isolation of a cDNA clone for hDHPR that spans the complete coding region, and present the nucleotide sequence and the predicted amino acid sequence. The hDHPR protein does not share extensive homology with the enzymatically related protein human dihydrofolate reductase. Patients with hDHPR deficiency were analysed for the presence of hDHPR cross-reacting protein, mRNA encoding hDHPR, and chromosomal DNA rearrangements. The results show that this inherited error of metabolism can result from a variety of mutations. However, no major rearrangements were seen in 11 patients analysed by Southern blotting. Three RFLPs were found with the restriction endonucleases AvaII and MspI. These RFLPs are useful for prenatal diagnosis of hDHPR deficiency.

Amino Acid Sequence↗
PubMed1985

Cranial computerized tomography in dihydropteridine reductase deficiency.

Dihydropteridine reductase deficiency is a rare cause of hyperphenylalaninaemia, characterized by severe and progressive neurological impairment, despite early and accurate dietary control of plasma phenylalanine. We describe two girls, diagnosed at 17 and 14 months of age, respectively, and immediately treated with L-dopa, 5-hydroxytryptophan and carbidopa. In spite of an adequate dietary and pharmacological treatment, the clinical and neurological pictures progressively worsened. Repeated cranial computerized axial tomography scans showed degeneration of the white matter and, in one case, calcification of the basal ganglia. The possible association of this last finding with folate depletion is discussed.

Amino Acid Metabolism, Inborn Errors↗
PubMed2000

NADH-ferric reductase activity associated with dihydropteridine reductase.

In mammals dietary ferric iron is reduced to ferrous iron for more efficient absorption by the intestine. Analysis of a pig duodenal membrane fraction revealed two NADH-dependent ferric reductase activities, one associated with a b-type cytochrome and the other not. Purification and characterization of the non-cytochrome ferric reductase identified a 31 kDa protein. MALDI-MS analysis and amino acid sequencing identified the ferric reductase as being related to the 26 kDa liver NADH-dependent quinoid dihydropteridine reductase (DHPR). The NADH-dependent DHPR ferric reductase activity was found to be pteridine-independent since exhaustive dialysis did not reduce activity and heat-inactivation destroyed activity. In intestinal Caco-2 cells, DHPR mRNA levels were found to be regulated by iron. Thus, DHPR appears to be a dual function enzyme, a NADH-dependent dihydopteridine reductase and an iron-regulated, NADH-dependent, pteridine-independent ferric reductase.

Animals↗
PubMed1994

Structural and mechanistic characteristics of dihydropteridine reductase: a member of the Tyr-(Xaa)3-Lys-containing family of reductases and dehydrogenases.

Dihydropteridine reductase (EC 1.6.99.7) is a member of the recently identified family of proteins known as short-chain dehydrogenases. When the x-ray structure of dihydropteridine reductase is correlated with conserved amino acid sequences characteristic of this enzyme class, two important common structural regions can be identified. One is close to the protein N terminus and serves as the cofactor binding site, while a second conserved feature makes up the inner surface of an alpha-helix in which a tyrosine side chain is positioned in close proximity to a lysine residue four residues downstream in the sequence. The main function of this Tyr-Lys couple may be to facilitate tyrosine hydroxyl group participation in proton transfer. Thus, it appears that there is a distinctive common mechanism for this group of short-chain or pyridine dinucleotide-dependent oxidoreductases that is different from their higher molecular weight counterparts.

Amino Acid Sequence↗
PubMed1992

Dihydropteridine reductase from Escherichia coli exhibits dihydrofolate reductase activity.

E. coli Dihydropteridine reductase, known to have a pterin-independent oxidoreductase activity with potassium ferricyanide as electron donor, has now been shown to possess also dihydrofolate reductase activity. The kinetic parameters for dihydrofolate reductase activity have been determined. The ratio of the three activities, dihydropteridine reductase, dihydrofolate reductase and pterin-independent oxidoreductase activity is 1.0, 0.05 and 4.3, respectively. The enzyme, a flavoprotein which is unstable in the presence of dithiothreitol, was shown to be a monomer with a molecular mass of 25.7 kDa. The apparent lack of discrimination between hydride transfer from the pyridine nucleotide to N5 of the pterin in the dihydropteridine reductase reaction and C6 of folate in the dihydrofolate reaction suggested that the FAD prosthetic group may be involved in the hydride transfers. The flavoprotein inhibitor N,N- dimethylpropargylamine inhibited the dihydropteridine reductase and oxidoreductase reactions differently and did not affect the dihydrofolate reductase activity however.

Dihydropteridine Reductase↗
PubMed1976

Isolation and characterization of dihydropteridine reductase from Pseudomonas species.

Dihydropteridine reductase isolated from the bacterium Pseudomonas species (ATCC 11299a) has been purified approximately 450-fold byammonium sulfate precipitation and diethylaminoethyl-cellulose chromatographic procedures. The preparation is at least 80% pure as judged by polyacrylamide gels. Its molecular weight was determined to be about 44,000. Both dihydropteridine reductase and phenylalanine hydroxylase activities were found to be higher in cells adapted to a medium containing L-phenylalanine or L-tyrosine as the sole carbon source than in those grown in L-asparagine. The substrate of the reductase is quinonoid dihydropteridine, and the product is tentatively identified as a tetrahydropteridine through its ability to serve as a cofactor for phenylalanine hydroxylase. The enzyme shows no marked specificity for the pteridine cofactor that occurs naturally in this organism, L-threo-neopterin. The pH optimum for the reductase is 7.2, and nicotinamide adenine dinucleotide, reduced form, is the preferred cosubstrate. Inhibition of the reduced and untreated enzyme by several sulfhydryl reagents was observed. A metal requirement for the reductase could not be demonstrated. Dihydropteridine reductase was found to be inhibited by aminopterin in a competitive manner with respect to the quinonoid dihydro form of 2-amino-4-hydroxy-6,7-dimethyl-5,6,7,8-tetrahydropteridine.

Aminopterin↗
PubMed1981

Inhibition of dihydropteridine reductase by dopamine.

Dihydropteridine reductase has been purified 900-fold from rat liver. Dopamine inhibited the enzyme up to 50% at a concentration of 0.11mm. In the presence of dopamine the enzyme gave non-hyperbolic v-against-[S] plots. This enzyme may have a role in control of dopamine biosynthesis.

Animals↗
PubMed1989

Quantitative structure-activity relationship study on some dihydropteridine reductase inhibitors.

The dihydropteridine reductase (DHPR) inhibitory potencies of some 4-phenyltetrahydropyridines, 4-phenylpiperidines, and 4-phenylpyridines, are analyzed in relation to their physico-chemical and molecular properties. They are found to have significant correlation with Hammett constant sigma and the van der Waals volume Vw. The correlation is linear with sigma and parabolic with Vw. Hence, it is argued that DHPR inhibition involves dispersion interaction and is enhanced by electron donation from the substituents but hindered by steric effects produced by large substituents. It is also found that these electronic and steric effects are significant only when they are produced by substituents being at specific position in the molecules.

Dihydropteridine Reductase↗
PubMed1982

Spectral studies of the interaction of the substrate 'quinonoid' 6-methyl dihydropterine and the coenzyme NADH used as marker in the dihydropteridine reductase assay.

In dihydropteridine reductase assay the substrate quinonoid dihydropterine is reduced again to tetrahydropterine, concomitantly oxidizing NADH, the indicator of the enzyme assay. Because of the strong oxidizing capacity of quinonoid dihydropterine, the degree of spontaneous oxidation of NADH by the various substances used in the dihydropterine reductase assay was studied spectrally. A high degree of spontaneous oxidation of NADH by the substrate itself was found, which can be regulated by dithiotreitol, dependent on its concentration. The absorbance increase at 336 nm, due to the non-quinonoid dihydropterine formed spontaneously from its quinonoid form, strongly interferes with the absorbance decrease at 340 nm, due to the disappearance of NADH. The interference results in a shift of the absorbance maximum of NADH from 340 nm up to higher wavelengths. This phenomenon, expressing itself in various ways in blank and sample, is discussed with relevance to the validity of the current enzyme assays used in a further classification of hyperphenylalaninaemic patients.

Buffers↗
PubMed2006

Mutations in the BH4-metabolizing genes GTP cyclohydrolase I, 6-pyruvoyl-tetrahydropterin synthase, sepiapterin reductase, carbinolamine-4a-dehydratase, and dihydropteridine reductase.

Tetrahydrobiopterin (BH(4)) deficiencies are a highly heterogeneous group of disorders with several hundred patients, and so far a total of 193 different mutant alleles or molecular lesions identified in the GTP cyclohydrolase I (GTPCH), 6-pyruvoyl-tetrahydropterin synthase (PTPS), sepiapterin reductase (SR), carbinolamine-4a-dehydratase (PCD), or dihydropteridine reductase (DHPR) genes. The spectrum of mutations causing a reduction in one of the three biosynthetic (GTPCH, PTPS, and SR) or the two regenerating enzymes (PCD and DHPR) is tabulated and reviewed. Furthermore, current genomic variations or SNPs are also compiled. Mutations in GCH1 are scattered over the entire gene, and only 5 out of 104 mutant alleles, present in a homozygous state, are reported to cause the autosomal recessive form of inheritable hyperphenylalaninemia (HPA) associated with monoamine neurotransmitter deficiency. Almost all other 99 different mutant alleles in GCH1 are observed together with a wild-type allele and cause Dopa-responsive dystonia (DRD, Segawa disease) in a dominant fashion with reduced penetrance. Compound heterozygous or homozygous mutations are spread over the entire genes for PTS with 44 mutant alleles, for PCBD with nine mutant alleles, and for QDPR with 29 mutant alleles. These mutations cause an autosomal recessive inherited form of HPA, mostly accompanied by a deficiency of the neurotransmitters dopamine and serotonin. Lack of sepiapterin reductase activity, an autosomal recessive variant of BH(4) deficiency presenting without HPA, was diagnosed in patients with seven different mutant alleles in the SPR gene in exons 2 or 3 or in intron 2. Details on all mutations presented here are constantly updated in the BIOMDB database (www.bh4.org).

Alcohol Oxidoreductases↗
PubMed1981

Isolation and characterization of dihydropteridine reductase from human liver.

Dihydropteridine reductase (EC 1.6.99.7) was purified from human liver obtained at autopsy by a three-step chromatographic procedure with the use of (1) a naphthoquinone affinity adsorbent, (2) DEAE-Sephadex and (3) CM-Sephadex. The enzyme was typically purified 1000-fold with a yield of 25%. It gave a single band on non-denaturing and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, and showed one spot on two-dimensional gel electrophoresis. The molecular weight of the enzyme was determined to be 50000 by sedimentation-equilibrium analysis and 47500 by gel filtration. On sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, a single subunit with mol.wt. 26000 was observed. A complex of dihydropteridine reductase with NADH was observed on gel electrophoresis. The isoelectric point of the enzyme was estimated to be pH 7.0. Amino acid analysis showed a residue composition similar to that seen for the sheep and bovine liver enzymes. The enzyme showed anomalous migration in polyacrylamide-gel electrophoresis. A Ferguson plot indicated that this behaviour is due to a low net charge/size ratio of the enzyme under the electrophoretic conditions used. The kinetic properties of the enzyme with tetrahydrobiopterin, 2-amino-4-hydroxy-6,7-dimethyl-5,6,7,8-tetrahydropteridine, NADH and NADPH are compared, and the effects of pH, temperature and a number of different compounds on catalytic activity are presented.

Amino Acids↗
PubMed1987

Rat striatal synaptosomes as a model system for studying the inhibition of dihydropteridine reductase activity.

The distribution of dihydropteridine reductase between soluble and particulate fractions in synaptosomes parallels that of lactate dehydrogenase, but not monoamine oxidase. Ki and I50 values for inhibitors obtained with the enzyme-rich P2 fraction and its twice-washed fraction (P2W2) were essentially the same, and were similar to those obtained with highly purified human liver enzyme. Dihydropteridine reductase inhibitory potency of multi-ring compounds containing a catechol-moiety was greater than that of single ring catecholic compounds, which in turn was greater than that of p-hydroxy-phenolic compounds. The P2 fraction of rat striatal synaptosomal preparations may serve as a convenient source of dihydropteridine reductase for studying the inhibition of this enzyme.

Animals↗
PubMed1991

Role of aspartate-37 in determining cofactor specificity and binding in rat liver dihydropteridine reductase.

Full-length rat dihydropteridine reductase (DHPR) cDNAs have been combined with a prokaryotic expression vector and introduced into Escherichia coli. Transformed bacteria express dihydropteridine reductase immunoreactive proteins and demonstrate conversion of quinonoid dihydropteridines to their tetrahydro forms. Several recombinant enzymes have been purified to homogeneity and biochemical studies have been carried out comparing their properties with those exhibited by the rat liver enzyme. The optimal reaction conditions, kinetic constants, and stability are similar for the recombinant and naturally occurring enzyme. The results indicate that the nonmutant recombinant rat DHPR is an authentic replica of the natural protein and that the characteristics of DHPR activity are determined by a single gene product and do not require specific modification via the eukaryotic cell. In addition to the wild type, three specific mutagenic forms of the reductase, A-6-V, W-104-F, and D-37-I, and an additional abbreviated structure have also been formed. Each of the products exhibits reductase activity, although they show varied affinities for their cofactor, NADH, and less stability to chromatography, dialysis, and concentration than the wild-type enzyme. The N-terminal sequence contains a classic NADH binding region between amino acids 9 and 36, and Asp 37 is essential for binding the cofactor as is shown by the approximately 20-fold increase in dissociation constant for the D-37-I mutant and diminished kcat (approximately 43 s-1 compared to 156 s-1 for the wild-type enzyme). The results indicate that the DHPR cofactor binding site is similar to typical dinucleotide requiring dehydrogenases such as lactic acid and liver alcohol dehydrogenase.

Amino Acid Sequence↗