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Ohashi A, Sugawara Y, Mamada K, Harada Y, Sumi T, Anzai N, Aizawa S, Hasegawa H. Membrane transport of sepiapterin and dihydrobiopterin by equilibrative nucleoside transporters: a plausible gateway for the salvage pathway of tetrahydrobiopterin biosynthesis. Mol Genet Metab 2011; 102:18-28. [PMID: 20956085 DOI: 10.1016/j.ymgme.2010.09.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2010] [Revised: 09/15/2010] [Accepted: 09/15/2010] [Indexed: 10/19/2022]
Abstract
Tetrahydrobiopterin (BH(4)) is synthesized de novo in particular cells, but in the case of a systemic or local BH(4) deficiency, BH(4) supplementation therapy is applied. BH(4)-responsive PKU has also been effectively treated with BH(4) supplementation. However, the rapid clearance of the supplemented BH(4) has prevented the therapy from being widely accepted. Deposition of BH(4) after supplementation involves oxidation of BH(4) to dihydrobiopterin (BH(2)) and subsequent conversion to BH(4) by the salvage pathway. This pathway is known to be almost ubiquitous in the body. However, the mechanism for the redistribution and exclusion of BH(4) across the plasma membrane remains unclear. The aim of this work was to search for the key transporter of the uptake precursor of the salvage pathway. Based on the observed sensitivity of pterin transport to nitrobenzylthioinosine (NBMPR), we examined the ability of ENT1 and ENT2, representative equilibrative nucleoside transporters, to transport sepiapterin (SP), BH(2) or BH(4) using HeLa cell and Xenopus oocyte expression systems. hENT2 was capable of transporting the pterins with an efficiency of SP>BH(2)>BH(4). hENT1 could also transport the pterins but less efficiently. Non-transfected HeLa cells and rat aortic endothelial cells were able to incorporate the pterins and accumulate BH(4) via uptake that is likely mediated by ENT2 (SP>BH(2)>BH(4)). When exogenous BH(2) was given to mice, it was efficiently converted to BH(4) and its tissue deposition was similar to that of sepiapterin as reported (Sawabe et al., 2004). BH(4) deposition after BH(2) administration was influenced by prior treatment with NBMPR, suggesting that the distribution of the administered BH(2) was largely mediated by ENT2, although urinary excretion appeared to be managed by other mechanisms. The molecular basis of the transport of SP, BH(2), and BH(4) across the plasma membrane has now been described for the first time: ENT2 is a transporter of these pterins and is a plausible gateway to the salvage pathway of BH(4) biosynthesis, at least under conditions of exogenous pterin supplementation. The significance of the gateway was discussed in terms of BH(2) uptake for BH(4) accumulation and the release for modifying the intracellular BH(2)/BH(4) ratio.
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Affiliation(s)
- Akiko Ohashi
- Department of Functional Morphology, Nihon University School of Medicine, Itabashi, Tokyo, 173-8610, Japan
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Nakamura K, Hasegawa H. Production and Peripheral Roles of 5-HTP, a Precursor of Serotonin. Int J Tryptophan Res 2009; 2:37-43. [PMID: 22084581 PMCID: PMC3195225 DOI: 10.4137/ijtr.s1022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Serotonin (5-hydroxytryptamine [5-HT]) has been implicated in a variety of physiological and pathological functions. Multiple steps of enzyme reactions enable biosynthesis of 5-HT. The first and rate-limiting step of the reaction is the synthesis of 5-hydroxy-L-tryptophan (5-HTP) from L-tryptophan. This step is dictated by an enzyme, tryptophan hydroxylase (TPH). TPH requires 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) as a co-substrate of TPH. 5-HTP has been simply regarded as a precursor of 5-HT and it is believed that the biological significance of 5-HTP is essentially ascribed to the production of 5-HT. However, recent works shed light on the specific functions of 5-HTP in the periphery. In this review article, we focus on the specific roles of exogenous 5-HTP as well as the endogenous 5-HTP in the gut epithelial cells. Since systemic treatment with 5-HTP is applied to patients with lower 5-HT levels, the studies on the specific role of 5-HTP might create an opportunity to explore the effects of exogenously-applied 5-HTP in the gut in man.
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Affiliation(s)
- Kazuhiro Nakamura
- Department of Pathology, Juntendo University School of Medicine, Tokyo 113-8421, Japan
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Sawabe K, Yamamoto K, Harada Y, Ohashi A, Sugawara Y, Matsuoka H, Hasegawa H. Cellular uptake of sepiapterin and push-pull accumulation of tetrahydrobiopterin. Mol Genet Metab 2008; 94:410-416. [PMID: 18511317 DOI: 10.1016/j.ymgme.2008.04.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2008] [Revised: 04/12/2008] [Accepted: 04/12/2008] [Indexed: 11/28/2022]
Abstract
Cellular uptake of sepiapterin resulted in an efficient accumulation of tetrahydrobiopterin. Tetrahydrobiopterin is much less permeable across the cell membrane than sepiapterin or dihydrobiopterin, the precursors of the tetrahydrobiopterin-salvage pathway. The uptake of sepiapterin by the cell was examined under metabolic arrest with N-acetylserotonin, an inhibitor of sepiapterin reductase. The release profile of previously accumulated sepiapterin was also analyzed. Two routes were clearly distinguishable, namely rapid and slow. Both were apparently bi-directional and equilibrating in type. Each route was connected to non-mixable pools somehow separated in the cell. The rapid process was too fast to analyze by the current methods of cell handling. The slower process was associated with conversion of sepiapterin to tetrahydrobiopterin in the absence of N-acetylserotonin, suggesting that this route opens into the cytosolic compartment where use of the salvage pathway was strongly driven by sepiapterin reductase and dihydrofolate reductase with a supply of NADPH which favors tetrahydrobiopterin accumulation. Consequently, sepiapterin was enforcedly taken up by the cell where it accumulated tetrahydrobiopterin in the cytosol in continuous manner.
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Affiliation(s)
- Keiko Sawabe
- Biotechnology Research Center, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan
| | - Kazumasa Yamamoto
- Biotechnology Research Center, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan
| | - Yoshinori Harada
- Department of Biosciences, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan
| | - Akiko Ohashi
- Department of Biosciences, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan
| | - Yuko Sugawara
- Department of Biosciences, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan
| | - Hiroshi Matsuoka
- Biotechnology Research Center, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan; Department of Biosciences, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan
| | - Hiroyuki Hasegawa
- Biotechnology Research Center, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan; Department of Biosciences, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan
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Brown GM. The biosynthesis of pteridines. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 35:35-77. [PMID: 4361155 DOI: 10.1002/9780470122808.ch2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Hasegawa H, Sawabe K, Nakanishi N, Wakasugi OK. Delivery of exogenous tetrahydrobiopterin (BH4) to cells of target organs: role of salvage pathway and uptake of its precursor in effective elevation of tissue BH4. Mol Genet Metab 2005; 86 Suppl 1:S2-10. [PMID: 16256391 DOI: 10.1016/j.ymgme.2005.09.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Revised: 08/24/2005] [Accepted: 09/10/2005] [Indexed: 11/30/2022]
Abstract
Cells in target organs such as liver do not generally incorporate tetrahydrobiopterin (BH4) in its fully reduced form. Instead, they transiently take up BH4 from the extracellular fluid, instantaneously oxidize it and then expel virtually all of it. However, a small but stable accumulation of BH4 was observed after BH4 administration to the cell cultures. This accumulation was inhibited by methotrexate, an inhibitor of dihydrofolate reductase, a phenomenon that was first suggested based on results of in vitro studies which used established cell lines such as RBL2H3 and PC12. These cells also take up dihydrobiopterin (BH2) and reduce it to enzymically active BH4. Their ability to accumulate usable BH4 upon BH4 administration was attributed to the incorporation of BH2, which in typical experiments was produced by the cells as well as by auto-oxidation of BH4. Most cells of the various cell lines so far examined behaved similarly in culture. Our in vivo work with individual mice demonstrated that administration of sepiapterin, BH2, and BH4 was comparably effective in raising BH4 levels in target organs. BH4 accumulation in various tissues after supplementation with BH4, BH2 or sepiapterin was also inhibited by methotrexate, as in the case of our cell culture system. It was concluded that the elevation in BH4 by supplementation was mainly through a "salvage pathway" that included BH2 as the key intermediate in the production of BH4 through the action of dihydrofolate reductase.
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Affiliation(s)
- Hiroyuki Hasegawa
- Department of Biosciences, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan.
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Sawabe K, Wakasugi KO, Hasegawa H. Tetrahydrobiopterin uptake in supplemental administration: elevation of tissue tetrahydrobiopterin in mice following uptake of the exogenously oxidized product 7,8-dihydrobiopterin and subsequent reduction by an anti-folate-sensitive process. J Pharmacol Sci 2004; 96:124-33. [PMID: 15467264 DOI: 10.1254/jphs.fp0040280] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
In order to increase the tissue level of tetrahydrobiopterin (BH4), supplementation with 6R-tetrahydrobiopterin (6RBH4) has been widely employed. In this work, the effectiveness of 6RBH4 was compared with 7,8-dihydrobiopterin (7,8BH2) and sepiapterin by administration to mice. Administration of 6RBH4 was the least effective in elevating tissue BH4 levels in mice while sepiapterin was the best. In all three cases, a dihydrobiopterin surge appeared in the blood. The appearance of the dihydrobiopterin surge after BH4 treatment suggested that systemic oxidation of the administered BH4 had occurred before accumulation of BH4 in the tissues. This idea was supported by the following evidences: 1) An increase in tissue BH4 was effectively inhibited by methotrexate, an inhibitor of dihydrofolate reductase which reduces 7,8BH2 to BH4. 2) When the unnatural diastereomer 6SBH4 was administered to mice, a large proportion of the recovered BH4 was in the form of the 6R-diastereomer, suggesting that this BH4 was the product of a dihydrofolate reductase process by which 7,8BH2 converts to 6RBH4. These results indicated that the exogenous BH4 was oxidized and the resultant 7,8BH2 circulated through the tissues, and then it was incorporated by various other tissues and organs through a pathway shared by the exogenous sepiapterin and 7,8BH2 in their uptake. It was demonstrated that maintaining endogenous tetrahydrobiopterin in tissues under ordinary conditions was also largely dependent on an methotrexate-sensitive process, suggesting that cellular tetrahydrobiopterin was maintained both by de novo synthesis and by salvage of extracellular dihydrobiopterin.
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Affiliation(s)
- Keiko Sawabe
- Department of Biosciences, Teikyo University of Science and Technology, Uenohara, Yamanashi 409-0193, Japan.
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Abstract
Rat erythrocyte sepiapterin reductase can catalyze the NADPH-dependent reduction of tetrahydropterin substrates with relative velocities of sepiapterin greater than lactoyltetrahydropterin greater than or equal to pyruvoyltetrahydropterin greater than 1'-hydroxy-2'-oxopropyltetrahydropterin; L-erythrotetrahydrobiopterin is the product of the reduction of all three tetrahydropterins. The 1' position of the 1',2'-diketone, pyruvoyltetrahydropterin, is reduced first; the product of this first reduction is 1'-hydroxy-2'-oxopropyltetrahydropterin. Both steps are inhibited by N-acetylserotonin. An antibody to sepiapterin reductase purified from rat erythrocytes was produced in rabbits, and the purified antibody is highly specific for sepiapterin reductase. This antibody is an inhibitor of both sepiapterin reductase activity and tetrahydrobiopterin biosynthesis in crude extracts of rat adrenal and brain. The antibody inhibits the production of both the biosynthetic intermediate, 1'-hydroxy-2'-oxopropyltetrahydropterin, and tetrahydrobiopterin. The results indicate that sepiapterin reductase is on the biosynthetic pathway to tetrahydrobiopterin, and catalyzes the complete reduction of pyruvoyltetrahydropterin to tetrahydrobiopterin. In contrast, homogenates of whole rat adrenal also produce large quantities of lactoyltetrahydropterin which suggests that in some tissues this compound may also be an intermediate in tetrahydrobiopterin biosynthesis. The synthesis of lactoyltetrahydropterin is not inhibited by the antibody to sepiapterin reductase and therefore does not appear to be catalyzed by sepiapterin reductase. However, sepiapterin reductase is responsible for the conversion of lactoyltetrahydropterin to tetrahydrobiopterin. The source of sepiapterin in biosynthetic reactions was found to be oxidative decomposition of lactoyltetrahydropterin.
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Tanaka K, Akino M, Hagi Y, Doi M, Shiota T. The enzymatic synthesis of sepiapterin by chicken kidney preparations. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)69709-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Krivi GG, Brown GM. Purification and properties of the enzymes from Drosophila melanogaster that catalyze the synthesis of sepiapterin from dihydroneopterin triphosphate. Biochem Genet 1979; 17:371-90. [PMID: 114165 DOI: 10.1007/bf00498976] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Sepiapterin synthase, the enzyme system responsible for the synthesis of sepiapterin from dihydroneopterin triphosphate, has been partially purified from extracts of the heads of young adult fruit flies (Drosophila melanogaster). The sepiapterin synthase system consists of two components, termed "enzyme A" (MW 82,000) and "enzyme B" (MW 36,000). Some of the properties of the enzyme system are as follows: NADPH and a divalent cation, supplied most effectively as MgCl2, are required for activity; optimal activity occurs are pH 7.4 and 30 C; the Km for dihydroneopterin triphosphate is 10 microM; and a number of unconjugated pterins, including biopterin and sepiapterin, are inhibitory. Dihydroneopterin cannot be used as substrate in place of dihydroneopterin triphosphate. Evidence is presented in support of a proposed reaction mechanism for the enzymatic conversion of dihydroneopterin triphosphate to sepiapterin in which enzyme A catalyzes the production of a labile intermediate by nonhydrolytic elimination of the phosphates of dihydroneopterin triphosphate, and enzyme B catalyzes the conversion of this intermediate, in the presence of NADPH, to sepiapterin. An analysis of the activity of sepiapterin synthase during development in Drosophila revealed the presence of a small amount of activity in eggs and young larvae and a much larger amount in late pupae and young adults. Sepiapterin synthase activity during development corresponds with the appearance of sepiapterin in the flies. Of a variety of eye color mutants of Drosophila melanogaster tested for sepiapterin synthase activity, only purple (pr) flies contained activity that was significantly lower than that found in the wild-type flies (22% of the wild-type activity). Further studies indicated that the amount of enzyme A activity is low in purple flies, whereas the amount of enzyme B activity is equal to that present in wild-type flies.
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Wilson TG, Jacobson KB. Mechanism of suppression in Drosophila. V. Localization of the purple mutant of Drosophila melanogaster in the pteridine biosynthetic pathway. Biochem Genet 1977; 15:321-32. [PMID: 405969 DOI: 10.1007/bf00484463] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The suppressible eye color mutant purple (pr) of Drosophila melanogaster is known to be unable to synthesize a wild-type complement of pteridine eye pigments. This study measures the reduced levels of drosopterins, sepiapterin, and an unidentified presumed pteridine in pr and prbw. Pteridine analyses in double mutants combining pr with one of three other eye color mutants sepia, Henna-recessive3, and prune2, suggest that the metabolic block in pr occurs prior to sepiapterin biosynthesis. Measurements of GTP and GTP cyclohydrolase in pr showed wild-type levels and indicate the metabolic block in pr to be at one of the steps converting dihydroneopterin triphosphate to sepiapterin. Quantitation of pteridines in suppressed purple [su(s)2; pr and pr; su(pr)e3] shows restoration of pteridines to wild-type or nearly wild-type levels.
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Eto I, Fukushima K, Shiota T. Enzymatic synthesis of biopterin from D-erythrodihydroneopterin triphosphate by extracts of kidneys from Syrian golden hamsters. J Biol Chem 1976. [DOI: 10.1016/s0021-9258(17)32976-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Fan CL, Krivi GG, Brown GM. The conversion of dihydroneopterin triphosphate to sepiapterin by an enzyme system from Drosophila melanogaster. Biochem Biophys Res Commun 1975; 67:1047-54. [PMID: 812500 DOI: 10.1016/0006-291x(75)90780-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Fukushima K, Eto I, Saliba D, Shiota T. The enzymatic synthesis of Crithidia active substance(s) and a phosphorylated D-erythroneopterin from GTP or GDP by liver preparations from Syrian golden hamsters. Biochem Biophys Res Commun 1975; 65:644-51. [PMID: 1148011 DOI: 10.1016/s0006-291x(75)80195-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Katoh S, Arai Y, Taketani T, Yamada S. Sepiapterin reductase in blood of various animals and of leukemic rats. BIOCHIMICA ET BIOPHYSICA ACTA 1974; 370:378-88. [PMID: 4548358 DOI: 10.1016/0005-2744(74)90099-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Fukushima T, Shiota T. Biosynthesis of Biopterin by Chinese Hamster Ovary (CHO K1) Cell Culture. J Biol Chem 1974. [DOI: 10.1016/s0021-9258(19)42439-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Descimon H. [Pieridae pterins and their biosynthesis of metabolism. IV. Pterin, xanthopterin and their hydrogenated derivatives in Colias croceus]. Biochimie 1973; 55:907-17. [PMID: 4772293 DOI: 10.1016/s0300-9084(73)80168-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Viscontini M, Furuta Y. [Pterin chemistry. 43. Synthesis of D-neopterin-3'-phosphate and D-neopterin-2',3'-cyclophosphate. Considerations on the biogenesis of biopterin]. Helv Chim Acta 1973; 56:1819-25. [PMID: 4744905 DOI: 10.1002/hlca.19730560546] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Smith-Gill SJ. Cytophysiological basis of disruptive pigmentary patterns in the leopard frog Rana pipiens. I. Chromatophore densities and cytophysiology. J Morphol 1973; 140:271-84. [PMID: 4541478 DOI: 10.1002/jmor.1051400303] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Kato S. Sepiapterin reductase from horse liver: purification and properties of the enzyme. Arch Biochem Biophys 1971; 146:202-14. [PMID: 4401291 DOI: 10.1016/s0003-9861(71)80057-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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