Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Sepiapterin”

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 55 records · Page 3Linked to original sources
PubMed1988

Sepiapterin reductase in human amniotic and skin fibroblasts, chorionic villi, and various blood fractions.

Sepiapterin reductase activity has been measured in amniotic fibroblasts by two procedures: one photometric and the other HPLC-fluorimetric. Both can be used for quantitative measurements, but the latter has considerable advantages including smaller standard deviation, much lower detection limit, and less volume of sample required. Sepiapterin reductase activity was also assayed in skin fibroblasts, chorionic villi and various blood fractions including stimulated mononuclear blood cells. Red blood cells have a low specific activity compared to unstimulated mononuclear blood cells, although the latter have a mean value with a high standard deviation. When the mononuclear blood cells were cultured for 5 days, the mean specific activity increased and the range became tighter. Enzyme stability and N-acetylserotonin inhibition were also studied.

Alcohol Oxidoreductases↗
PubMed1994

Phosphorylation by Ca2+/calmodulin-dependent protein kinase II and protein kinase C of sepiapterin reductase, the terminal enzyme in the biosynthetic pathway of tetrahydrobiopterin.

Sepiapterin reductase, the terminal enzyme in the biosynthetic pathway of tetrahydrobiopterin, was stoichiometrically phosphorylated by Ca2+/calmodulin-dependent protein kinase II and protein kinase C (Ca2+/phospholipid-dependent protein kinase) in vitro. Maximal incorporation of phosphate into the enzyme subunit by these was 3.05 +/- 0.05 (n = 4) and 0.74 +/- 0.03 (n = 5) 32P mol per mol enzyme subunit, respectively. The enzyme was not phosphorylated by cyclic nucleotide-dependent protein kinase of either the cAMP-dependent or cGMP-dependent type in this study. Dihydropteridine reductase, another enzyme working in direct supply of tetrahydrobiopterin, was also a good substrate for Ca2+/calmodulin-dependent protein kinase II. Phosphorylation of sepiapterin reductase by these protein kinases modified the kinetic properties of the enzyme. It is likely that these multifunctional Ca(2+)-activated protein kinases may play a role in the regulation of the physiological function of the BH4-generating enzymes in vivo, as was previously found in the case of BH4-requiring enzymes.

Alcohol Oxidoreductases↗
PubMed1995

Mouse sepiapterin reductase: an enzyme involved in the final step of tetrahydrobiopterin biosynthesis. Primary structure deduced from the cDNA sequence.

We carried out the cloning of a mouse cDNA encoding a sepiapterin reductase which is involved in the final step of tetrahydrobiopterin biosynthesis as a first step toward gene-targeting technique in mice. The sequence contained 1245 nucleotides consisting of an open reading frame of 783 nucleotides encoding a protein of 261 amino acid residues whose molecular weight was 27,851, a 5'-untranslated region of 21 nucleotides and a 3'-untranslated region of 441 nucleotides containing poly(A) tail. The amino acid sequence of mouse sepiapterin reductase revealed the identity of 88% with rat and 74% with human sequence.

Alcohol Oxidoreductases↗
PubMed2005

Sepiapterin attenuates 1-methyl-4-phenylpyridinium-induced apoptosis in neuroblastoma cells transfected with neuronal NOS: role of tetrahydrobiopterin, nitric oxide, and proteasome activation.

In this study, we investigated the molecular mechanism of toxicity of 1-methyl-4-phenylpyridinium (MPP+), an ultimate toxic metabolite of a mitochondrial neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, that causes parkinsonism in experimental animals and humans. Using wild-type and human neuronal nitric oxide synthase (nNOS) stably transfected neuroblastoma cells (SH-SY5Y), we showed that nNOS overexpression in SH-SY5Y cells greatly enhanced proteasome activity and mitigated MPP+-induced apoptosis. During MPP+-induced oxidative stress, intracellular BH4 levels decreased, resulting in nNOS "uncoupling" (i.e., switching from nitric oxide to superoxide generation). Increasing the intracellular BH4 levels by sepiapterin supplementation restored the nNOS activity, inhibited superoxide formation, increased proteasome activity, decreased protein ubiquitination, and attenuated apoptosis in MPP+-treated cells. Implications of BH4 depletion in dopaminergic cells and sepiapterin supplementation to augment the striatal nNOS activity in the pathogenesis mechanism and treatment of Parkinson disease are discussed.

1-Methyl-4-phenylpyridinium↗
PubMed2006

Sepiapterin reductase deficiency: clinical presentation and evaluation of long-term therapy.

Sepiapterin reductase deficiency has recently been recognized as a treatable, inborn error of pterin metabolism. This investigation is the first long-term clinical study demonstrating impressive positive, long-term effects of treatment in two cases of sepiapterin reductase deficiency after 2 and 5 years of treatment respectively. The two patients were not diagnosed before 7 and 13 years of age. These results highlight the importance of cerebrospinal fluid neurotransmitter investigations in childhood encephalopathy, in cases of unexplained early-onset neurologic handicap. Such a widened approach to the diagnostic efforts in early-onset encephalopathy with motor delay during childhood is important, as we have at our disposal a simple and effective treatment.

5-Hydroxytryptophan↗
PubMed1987

Sepiapterin reductase in cultured human cells.

Sepiapterin reductase, an enzyme involved in the synthesis of tetrahydrobiopterin (the natural cofactor for phenylalanine, tyrosine and tryptophan hydroxylases), has been assayed in cultured human amniotic fibroblasts and in cultured mononuclear blood cells. In both cases, the Michaelis constants for sepiapterin and NADPH were essentially equal; 20 microM and 6 microM respectively for stimulated mononuclear blood cells and 22 microM and 5 microM respectively for amniotic fibroblasts. The inhibition by N-acetylserotonin was also similar in both cases. The concentration that produced 50% inhibition in stimulated mononuclear blood cells and in amniotic fibroblasts was 2 microM. The results strongly suggest that the same enzyme is acting in both types of cells, at least when grown in culture.

Alcohol Oxidoreductases↗
PubMed2002

Mutational analysis of sites in sepiapterin reductase phosphorylated by Ca2+/calmodulin-dependent protein kinase II.

Sepiapterin reductase (SPR) catalyzes the last step in the pathway of tetrahydrobiopterin biosynthesis in tissues. SPR is phosphorylated by Ca2+-dependent protein kinases, which indicates that Ca2+-activated protein kinases may play a role in the regulation of SPR in vivo. Phosphorylation sites of rat sepiapterin reductase (rSPR) by Ca2+/calmodulin-dependent protein kinase II were determined in the present study. Using specific monoclonal anti-phospho-Ser and -Thr antibodies, we found that only Ser residues of rSPR were phosphorylated. We constructed several point mutants of SPR by systematically replacing the three Ser residues by Ala ones. These mutants showed that all three Ser residues, i.e. S46, S196, and S214, of rSPR were phosphorylated. We also recognized that only Ser-213 of human SPR was phosphorylated. Each of these serine residues in SPR was found in the consensus sequence (Arg-X-X-Ser/Thr) of the phosphorylation site.

Alcohol Oxidoreductases↗
PubMed1999

Functionally important residues tyrosine-171 and serine-158 in sepiapterin reductase.

The active site of sepiapterin reductase (SPR), which is a member of the NADP(H)-preferring short-chain dehydrogenase/reductase (SDR) family and acts as the terminal enzyme in the biosynthetic pathway of tetrahydrobiopterin cofactor (BH4), was investigated by truncation and site-directed mutagenesis. The truncation mutants showed that N-terminal and C-terminal residues contribute to bind coenzyme and substrate, respectively. The mutant rSPRA29V showed decreased activity; however, the A-X-L-L-S sequence, which has been reported as a putative pterin binding site, was estimated to preferably work as a component in the region for binding coenzyme rather than substrate. Site-directed mutants of rSPRS158D, rSPRY171V, and rSPRK175I showed low, but significant, activity having similar Km values and kcat/Km values less than 25%, for both sepiapterin and NADPH. Both amino acids Tyr-171 and Ser-158 are located within a similar distance to the carbonyl group of the substrate in the crystal structure of mouse SPR, and the double point mutant rSPRY171V+S158D was indicated to be inactive. These results showed that Ser-158, Tyr-171, and Lys-175 contributed to the catalytic activity of SPR, and both Tyr-171 and Ser-158 are simultaneously necessary on proton transfer to the carbonyl functional groups of substrate.

Alcohol Oxidoreductases↗
PubMed1982

Biosynthesis, nonenzymatic synthesis, and purification of the intermediate in synthesis of sepiapterin in Drosophila.

The enzymatic conversion of the D-erythro-dihydroneopterin triphosphate [H2-neopterin-(P)3] to sepiapterin occurs via a nonphosphorylated intermediate as shown by others. We have developed a high-performance liquid chromatography assay for this intermediate and have found that the intermediate (X) and two related compounds (X1 and X2) can be formed nonenzymatically under certain conditions from H2-neopterin-(P)3. The reaction is catalyzed by tris(hydroxymethyl)aminomethane, dependent upon H2-neopterin-(P)3 concentration, significant at temperatures greater than 80 degrees C, and maximal between pH 8.5 and 9.5 (as determined at 25 degrees C). All three compounds were purified, and it was found that both X and X1 can serve as substrates for the enzymatic, NADPH-dependent synthesis of sepiapterin. From the kinetics of formation from H2-neopterin-(P)3 and the similarity of the ultraviolet spectra, it is clear that X, X1, and X2 are closely related compounds. None of the three compounds is reduced by NaBH4; only X1 is sensitive to periodate oxidation. All three can be oxidized with iodine to give rise to highly fluorescent compounds that in turn can be reduced by NaBH4 to give rise to the respective parent compounds. These latter observations indicate that X, X1, and X2 are dihydropterins. These results are discussed relative to the proposed structures for enzymatically produced X. The methods described for the nonenzymatic synthesis of X and its purification should allow preparation of large amounts of X for future study.

Drosophila↗
PubMed2003

Tetrahydrobiopterin precursor sepiapterin provides protection against neurotoxicity of 1-methyl-4-phenylpyridinium in nigral slice cultures.

Complex-I inhibition and oxidative processes have been implicated in the loss of nigral dopamine neurones in Parkinson's disease and the toxicity of MPTP and its metabolite MPP+. Tetrahydrobiopterin, an essential cofactor for tyrosine hydroxylase, may act as an antioxidant in dopaminergic neurones and protects against the toxic consequences of glutathione depletion. Here we studied the effects of manipulating tetrahydrobiopterin levels on MPP+ toxicity in organotypic, rat ventral mesencephalic slice cultures. In cultures exposed to 30 micro m MPP+ for 2 days, followed by 8 days 'recovery' in control medium, we measured dopamine and its metabolites in the tissue and culture medium by HPLC, lactate dehydrogenase release to the culture medium, cellular uptake of propidium iodide and counted the tyrosine hydroxylase-immunoreactive neurones. Inhibition of tetrahydrobiopterin synthesis by 2,4-diamino-6-hydroxypyrimidine had no significant synergistic effect on MPP+ toxicity. In contrast, the tetrahydrobiopterin precursor l-sepiapterin attenuated the MPP+-induced dopamine depletion and loss of tyrosine hydroxylase-positive cells in a dose-dependent manner with 40 micro m l-sepiapterin providing maximal protection. Accordingly, increasing intracellular tetrahydrobiopterin levels may protect against oxidative stress by complex-I inhibition.

1-Methyl-4-phenylpyridinium↗
PubMed1988

Coenzyme stimulation of isomerase activity of sepiapterin reductase in the biosynthesis of tetrahydrobiopterin.

The 6-lactoyl tetrahydropterin (C1'-keto PH4) isomerase activity of sepiapterin reductase, which was found in our recent work (Katoh and Sueoka (1987) J. Biochem. 101, 275-278) as a novel activity of the enzyme, i.e., the conversion of C1'-keto PH4 to 6-1'-hydroxy-2'-oxopropyl tetrahydropterin (C2'-keto PH4) without coenzymes, could be enhanced by a small amount of NADPH or NADP+. The concentration of NADP+ required for the maximal stimulation was approximately the same as the concentration of the enzyme subunit. When NADP+ was added with the enzyme and C1'-keto PH4 at pH 8.6, the reaction sequence of C1'-keto PH4----C2'-keto PH4----tetrahydrobiopterin (BH4) was observed in the presence of dithioerythritol. These observations suggest that the coenzyme stimulating the isomerase function of sepiapterin reductase may be involved in the two sequential reductions, from pyruvoyl tetrahydropterin to BH4, by causing internal rearrangement of the keto group of the first intermediate, C1'-keto PH4, to form the second one, C2'-keto PH4.

Alcohol Oxidoreductases↗
PubMed2005

DAF-FM (4-amino-5-methylamino-2',7'-difluorofluorescein) diacetate detects impairment of agonist-stimulated nitric oxide synthesis by elevated glucose in human vascular endothelial cells: reversal by vitamin C and L-sepiapterin.

Elevated plasma glucose, as commonly seen in types I and II diabetes mellitus, is known to result in endothelial dysfunction, a condition characterized by a loss of nitric oxide (NO)-dependent regulation of vascular tone. In the present study, we have utilized a recently developed NO-sensitive fluorescent dye, DAF-FM (4-amino-5-methylamino-2',7'-difluorofluorescein) diacetate to directly examine the consequences of elevated glucose on agonist-evoked NO synthesis in cultured human vascular endothelial cells. Exposure of cells for 5 to 7 days to high (20 mM) external glucose markedly reduced NO production in response to ATP, histamine, or the calcium ionophore calcimycin A23187 compared with 5 and 10 mM glucose concentrations. However, high glucose did not affect agonist-evoked elevations in cytosolic-free calcium, as monitored by Fluo-3. The addition of vitamin C (150 microM) and L-sepiapterin (20 microM) for approximately 24 h to 20 mM glucose-treated cells improved stimulus-evoked NO synthesis but had no effect on cells exposed to either 5 or 10 mM glucose. Likewise, impaired NO production in high glucose-treated cells was largely reversed by exposure ( approximately 3 h) to superoxide dismutase. Cellular levels of endothelial nitric-oxide synthase protein were unaltered by elevated glucose treatment, and no further change was observed after the addition of vitamin C and l-sepiapterin. Taken together, the results of our study serve to directly explain at the cellular level how glucose-impaired NO production in human endothelial cells may be reversed by agents that are reported clinically to improve endothelium-dependent vasorelaxation in patients.

Adenosine Triphosphate↗
PubMedDate not supplied

Lack of nitric oxide mediation of flow-dependent arteriolar dilation in type I diabetes is restored by sepiapterin.

The mechanisms leading to microangiopathy in diabetes mellitus have still not been clearly elucidated. We hypothesized that type I diabetes mellitus affects the endothelium and alters flow-dependent dilation of arterioles, an important mechanism involved in local regulation of blood flow. Isolated, pressurized gracilis muscle arterioles (inside diameter approximately 150 microm at 80 mm Hg) from rats with streptozotocin (STZ)-induced diabetes mellitus exhibited reduced dilations induced by increases in perfusate flow compared to those of normal rats (plasma glucose: 25.7 +/- 0.7 vs. 6.4 +/- 0.5 mmol/l; maximum increase in diameter: 15 +/- 4 vs. 31+/- 3 microm, p < 0.05). In control arterioles, both nitric oxide (NO) and prostaglandins mediated the flow-dependent dilation, whereas flow-induced dilations of diabetic arterioles were unaffected by N(omega)-nitro-L-arginine methyl ester (L-NAME) and were abolished by indomethacin. Sepiapterin - precursor of the endothelial NO synthase (eNOS) cofactor tetrahydrobiopterin (BH(4)) - restored the L-NAME-sensitive portion of flow-dependent dilations of diabetic arterioles. Furthermore, depletion of BH(4) by 2,4-diamino-6-hydroxypyrimidine (DAHP) in control arterioles also resulted in reduced flow-dependent dilations, which were restored by intraluminal sepiapterin [but not with superoxide dismutase (SOD) plus catalase (CAT) (SOD+CAT)] and then could be inhibited by L-NAME. Dilations induced by the NO donor sodium nitroprusside (SNP) were unaffected by L-NAME in diabetes mellitus arterioles or when eNOS was activated by intraluminal flow in DAHP-treated arterioles (with or without SOD+CAT). In contrast, pyrogallol (known to produce reactive oxygen species) substantially reduced acetylcholine- and SNP-induced dilation in a SOD+CAT-reversible manner. Collectively, these findings suggest that in diabetic arterioles, due to the reduced bioavailability of BH(4), the synthesis of NO by eNOS is limited, resulting in a reduced flow-induced dilation, a mechanism that may also be responsible for the development of diabetic microangiopathy and exacerbation of other vascular diseases.

Acetylcholine↗
PubMed1992

The properties of monoclonal antibody against sepiapterin reductase from fat body of the silkworm, Bombyx mori.

A specific monoclonal antibody prepared for the 29-kDa a subunit of silkworm fat body sepiapterin reductase (SPR) was able to recognize the subunit in crude extract of fat body after SDS treatment. Although SPR from the silkworm fat body has biochemical properties similar to those reported for SPR from mammalian sources, especially rat erythrocytes, the antibody failed to recognize the 28-kDa subunit of rat erythrocyte SPR. This result indicates that SPR from silkworm fat body has a different amino-acid sequence from that of the rat erythrocyte enzyme. Sepiapterin reductase activity has not been found in crude extract of fat body from the silkworm mutant lemon. Although the antibody recognized only 29-kDa protein in the crude extract of silkworm fat body from normal strain after SDS-treatment, the antibody recognized only an approximately 80-kDa protein in the crude extract of the lemon mutant after SDS-treatment.

Alcohol Oxidoreductases↗
PubMed1992

New inhibitors of sepiapterin reductase. Lack of an effect of intracellular tetrahydrobiopterin depletion upon in vitro proliferation of two human cell lines.

N-Acetylserotonin (compound 1) and N-acetyldopamine (compound 7) inhibit bovine adrenal medullary sepiapterin reductase in a manner competitive with the pterin substrate and have Ki values of 0.12 and 0.4 microM, respectively. Molecular modeling suggests that the phenyl rings of the two compounds bind in the pyrimidine pocket of the enzyme with the 3-hydroxyl of dopamine or the 5-hydroxyl of serotonin aligned at the pyrimidine 4-position. Further, the acetyl moieties of the two inhibitors appear to mimic the substrate side chain. Consistent with this analysis, N-acetyl-m-tyramine (compound 13) is also an excellent competitive inhibitor (Ki = 0.13 microM), whereas N-acetyltryptamine (compound 2), N-acetyl-p-tyramine (compound 14) and N-acetylphenylethylamine (compound 15) all bind poorly. Interestingly, restricted-rotation analogs of N-acetyldopamine and N-acetyl-m-tyramine are noncompetitive inhibitors of the enzyme. Modification of N-acetyldopamine to N-chloroacetyldopamine (compound 10) or of N-acetylserotonin to the N-chloroacetyl (5) or N-methoxyacetyl (compound 6) analogs results in greatly increased competitive affinity, with Ki = 0.014 microM for the dopamine analog and 0.006 and 0.008 microM, respectively, for the serotonin analogs. In MOLT-4 T-cell leukemia and MCF-7 breast adenocarcinoma in culture, 0.1 mM N-methoxyacetylserotonin depleted tetrahydrobiopterin by greater than or equal to 97 and greater than 50%, respectively, with no effect upon cell growth. In both cell lines, the GTP cyclohydrolase inhibitor, 2,4-diamino-6-hydroxypyrimidine at 1-5 mM also depleted tetrahydrobiopterin greater than or equal to 97%. In this case, however, modest growth inhibition did occur. Since the growth inhibition could not be reversed upon tetrahydrobiopterin repletion, inhibition was due to other effects of the inhibitor rather than to tetrahydrobiopterin depletion. The results show that there is no effect on cell growth when at least 97% of the tetrahydrobiopterin in these cell lines is depleted. Since the sepiapterin reductase inhibitor depleted tetrahydrobiopterin with fewer nonspecific effects than the cyclohydrolase inhibitor, it will be useful for determining metabolic effects of tetrahydrobiopterin depletion.

Alcohol Oxidoreductases↗
PubMed1990

Tetrahydrobiopterin biosynthetic activities in human macrophages, fibroblasts, THP-1, and T 24 cells. GTP-cyclohydrolase I is stimulated by interferon-gamma, and 6-pyruvoyl tetrahydropterin synthase and sepiapterin reductase are constitutively present.

Interferon-gamma induces tetrahydrobiopterin biosynthesis in human cells and cell lines. Macrophages are peculiar in the formation of large amounts of neopterin derivatives as compared to tetrahydrobiopterin (Werner, E. R., Werner-Felmayer, G., Fuchs, D., Hausen, A., Reibnegger, G., and Wachter, H. (1989) Biochem J. 262, 861-866). Here we compare the impact of interferon-gamma treatment on activities of GTP-cyclohydrolase I (EC 3.5.4.16), 6-pyruvoyl tetrahydropterin synthase, and sepiapterin reductase (EC 1.1.1.153) in human peripheral blood-derived macrophages, normal dermal fibroblasts, THP-1 myelomonocytic cells, and the T 24 bladder transitional-cell carcinoma line. Upon interferon-gamma treatment, GTP-cyclohydrolase I activity is increased 7- to 40-fold, whereas 6-pyruvoyl tetrahydropterin synthase and sepiapterin reductase activities, which are constitutively present in all four investigated cells, remain unchanged. In fibroblasts and T 24 cells GTP cyclohydrolase I activity is the rate-limiting step of tetrahydrobiopterin biosynthesis. In macrophages and in THP-1 cells, however, the induced GTP cyclohydrolase I activity is higher than the 6-pyruvoyl tetrahydropterin synthase activity, leading to the accumulation of neopterin and neopterin phosphates.

Alcohol Oxidoreductases↗
PubMed1985

Biosynthesis of neopterin, sepiapterin, and biopterin in rat and human ocular tissues.

Neopterin, sepiapterin, and biopterin synthesis by lens, retina, and ciliary body-iris of rat and human indicates pteridine formation from their precursor, GTP. The pteridine biosynthesis was higher in the retina (neopterin 422 +/- 27, 260 +/- 24; sepiapterin 135 +/- 12, 118 +/- 14; biopterin 76 +/- 10, 68 +/- 8 nanomoles/g soluble protein/hr, in rat and human, respectively) than in the ciliary body-iris and lens. The light-sensitive pteridines may protect eye tissues against the effects of sunlight in addition to their role in the hydroxylation of aromatic amino acids.

Animals↗
PubMed1998

Genomic organization and chromosomal localization of the human sepiapterin reductase gene.

Sepiapterin reductase (SPR) catalyzes the final step of the biosynthetic pathway of tetrahydrobiopterin, which is an essential cofactor for aromatic amino acid hydroxylases and nitric oxide synthases. To aid the analysis of any possible human diseases caused by mutations in SPR, we have cloned and characterized the human SPR gene. The gene is composed of three exons spanning approximately 4 kilobases. The transcriptional starting point was determined around the cytosine nucleotide at position -81 by primer extension and RT-PCR analyses. There was no typical TATA-box within 300 bp from the transcriptional starting point. We found the Sp1-binding consensus sequence in the 5'-flanking region. The human SPR gene was mapped to chromosome band 2p13 by fluorescence in situ hybridization.

Alcohol Oxidoreductases↗