Tetrahydrobiopterin biosynthesis. Studies with specifically labeled (2H)NAD(P)H and 2H2O and of the enzymes involved

Curtius, Hans−Christoph; Heintel, Dorothee; Ghisla, Sandro; Kuster, Thomas; Leimbacher, Walter; Niederwieser, A.

doi:10.1111/j.1432-1033.1985.tb08855.x

Cited by 51 publications

(19 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, it is likely that net BH4 cellular bioavailability reflects the balance between de novo BH4 synthesis, loss of BH4 by oxidation to BH2, and regeneration of BH4 by DHFR. In human liver extracts, DHFR has been shown to reduce BH2 to BH4 as part of the salvage pathway for biopterin synthesis [10]. Recent studies have investigated the recycling function of DHFR in cultured endothelial cells.…”

mentioning

confidence: 99%

Dihydrofolate reductase protects endothelial nitric oxide synthase from uncoupling in tetrahydrobiopterin deficiency

Crabtree

Hale

Channon

2011

Free Radical Biology and Medicine

105

View full text Add to dashboard Cite

Tetrahydrobiopterin (BH4) is a required cofactor for the synthesis of NO by endothelial nitric oxide synthase (eNOS), and endothelial BH4 bioavailability is a critical factor in regulating the balance between NO and superoxide production (eNOS coupling). Biosynthesis of BH4 is determined by the activity of GTP-cyclohydrolase I (GTPCH). However, BH4 levels may also be influenced by oxidation, forming 7,8-dihydrobiopterin (BH2), which promotes eNOS uncoupling. Conversely, dihydrofolate reductase (DHFR) can regenerate BH4 from BH2, but whether DHFR is functionally important in maintaining eNOS coupling remains unclear. To investigate the mechanism by which DHFR might regulate eNOS coupling in vivo, we treated wild-type, BH4-deficient (hph-1), and GTPCH-overexpressing (GCH-Tg) mice with methotrexate (MTX), to inhibit BH4 recycling by DHFR. MTX treatment resulted in a striking elevation in BH2 and a decreased BH4:BH2 ratio in the aortas of wild-type mice. These effects were magnified in hph-1 but diminished in GCH-Tg mice. Attenuated eNOS activity was observed in MTX-treated hph-1 but not wild-type or GCH-Tg mouse lung, suggesting that inhibition of DHFR in BH4-deficient states leads to eNOS uncoupling. Taken together, these data reveal a key role for DHFR in regulating the BH4 vs BH2 ratio and eNOS coupling under conditions of low total biopterin availability in vivo.

show abstract

mentioning

confidence: 99%

Dihydrofolate reductase protects endothelial nitric oxide synthase from uncoupling in tetrahydrobiopterin deficiency

Crabtree

Hale

Channon

2011

Free Radical Biology and Medicine

105

View full text Add to dashboard Cite

show abstract

“…1). PTP synthase modifies the carbohydrate side chain of dihydroneopterin triphosphate, a substrate similar to those utilized by aldolase, and the proposed PTP synthase reaction mechanisms (8,40) include eneamine intermediates similar to those formed in aldolase-catalyzed reactions. We therefore tested the possibility that ARP might be PTP synthase by in situ hybridization to the salivary gland polytene chromosomes.…”

Section: Resultsmentioning

confidence: 99%

Alternate use of divergent forms of an ancient exon in the fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster.

et al. 1992

View full text Add to dashboard Cite

The fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster contains three divergent copies of an evolutionarily conserved 3' exon. Two mRNAs encoding aldolase contain three exons and differ only in the poly(A) site. The first exon is small and noncoding. The second encodes the first 332 amino acids, which form the catalytic domain, and is homologous to exons 2 through 8 of vertebrates. The third exon encodes the last 29 amino acids, thought to control substrate specificity, and is homologous to vertebrate exon 9. A third mRNA substitutes a different 3' exon (4a) for exon 3 and encodes a protein very similar to aldolase. A fourth mRNA begins at a different promoter and shares the second exon with the aldolase messages. However, two exons, 3a and 4a, together substitute for exon 3. Like exon 4a, exon 3a is homologous to terminal aldolase exons. The exon 3a-4a junction is such that exon 4a would be translated in a frame different from that which would produce a protein with similarity to aldolase. The putative proteins encoded by the third and fourth mRNAs are likely to be aldolases with altered substrate specificities, illustrating alternate use of duplicated and diverged exons as an evolutionary mechanism for adaptation of enzymatic activities.Fructose-1,6-bisphosphate (FBP) aldolase (EC 4.1.2.13) is a glycolytic enzyme that catalyzes reversible aldol cleavage of FBP to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Aldolases from vertebrates, plants, microorganisms, and Drosophila spp. have been characterized (17). The enzymes from higher eukaryotes, including Drosophila spp., are type I aldolases, which function as tetramers and form a Schiffs base between the substrate and an active-site lysine residue. In vertebrates, three isozymes, A, B, and C, are expressed in different tissues. The Drosophila enzyme displays 60 to 70% sequence identity with the mammalian enzymes and is most related to the type A muscle forms (27). Drosophila enzyme subunits (39 kDa) can form functional heterotetramers with certain mammalian enzymes (4), indicating a high degree of functional conservation.Several mammalian aldolase genes (5,19,21,38,42,43) and a chicken aldolase gene (6) have been characterized, revealing close structural relationships between the genes encoding the different isozymes within a species and between the genes encoding equivalent isozymes in different species. The intron-exon organization is identical in all characterized vertebrate genes.In this report, we describe the organization of the aldolase gene of Drosophila melanogaster, which shares structural features with the vertebrate genes. The Drosophila gene appears unique in that it produces transcripts with alternate 3' ends, including one with two exons substituted for the terminal exon of the aldolase-encoding mRNAs. All terminal exons are related evolutionarily to the terminal exons of vertebrate aldolase-encoding mRNAs. The unique mRNAs, if translated, could produce aldolase-related proteins that * Corresponding author.contain th...

show abstract

“…Using purified sepiapterin reductase from rat erythrocytes the latter was shown to be specific for the pro-S hydrogen of NADPH (17), while PPH 4 reductase from human liver appears to use the pro-R hydrogen of NADPH. This different stereospecificity is of importance since BH 4 formation from NH1TP catalyzed by partially purified human liver extracts leads to incorporation of the 4-pro-S hydrogen of NADPH at each of the C(1 ') and C(2') positions of BH 4 (17). This suggests that sepiapterin reductase is the sole enzyme responsible for PPH 4 reduction.…”

Section: Polyclonal Antiserum To Human Pph 4 Reductasementioning

confidence: 99%

Purification and Characterization of a Carbonyl Reductase from Human Liver, which is Competent in the Reduction of 6-Pyruvoyl-Tetrahydropterin

Steinerstauch

Sawada²,

Leimbacher

et al. 1989

Pteridines

Self Cite

View full text Add to dashboard Cite

SummaryAn enzyme which reduces 6-pyruvoyl-tetrahydropterin has been purified to apparent homogeneity from human liver. It consists of a single polypeptide chain with a molecular weight of 35 kDa, has an isoelectric point of 5.9 ± 0.1 and contains no glycosyl residues. The pure enzyme has a specific activity of 450 mU/mg protein at pH 7.0 in 10 mM potassium phosphate buffer. It converts 6-pyruvoyl-tetrahydropterin to 6-lactoyltetrahydropterin by transfer of the pro 4R-hydrogen of NADPH to form the side chain -OH at position C(2') of the substrate. Km values are 1.8 IlM for 6-pyruvoyl-tetrahydropterin and 5.5 IlM for NADPH. Polyclonal antibodies raised against the purified enzyme recognize 6-pyruvoyl-tetrahydropterin reductase in Western blot and ELISA but do not cross-react with human sepiapterin reductase. The enzyme appears to be identical with aldose reductase.

show abstract

Tetrahydrobiopterin biosynthesis. Studies with specifically labeled (2H)NAD(P)H and 2H2O and of the enzymes involved

Cited by 51 publications

References 24 publications

Dihydrofolate reductase protects endothelial nitric oxide synthase from uncoupling in tetrahydrobiopterin deficiency

Dihydrofolate reductase protects endothelial nitric oxide synthase from uncoupling in tetrahydrobiopterin deficiency

Alternate use of divergent forms of an ancient exon in the fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster.

Purification and Characterization of a Carbonyl Reductase from Human Liver, which is Competent in the Reduction of 6-Pyruvoyl-Tetrahydropterin

Contact Info

Product

Resources

About