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Results for “PHENYLPYRUVIC ACID”

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At least 469 records · Page 26Linked to original sources
PubMed1997

Determination of p-hydroxyphenylpyruvate, p-hydroxyphenyllactate and tyrosine in normal human plasma by gas chromatography-mass spectrometry isotope-dilution assay.

The synthesis and purification of [13C2]p-hydroxyphenyllactic acid from [13C2]p-hydroxyphenylpyruvic acid, the characterization of tert.-butyldimethylsilyl-derivatized tyrosine, p-hydroxyphenylpyruvic acid and p-hydroxyphenyllactic acid, and an isotope-dilution assay for these substances in normal human plasma using gas chromatography-mass spectrometry (GC-MS) are described. Using this method plasma p-hydroxyphenylpyruvate, p-hydroxyphenyllactate and tyrosine levels of 68 +/- 42 ng/ml, 118 +/- 45 ng/ml and 16.6 +/- 6.3 micrograms/ml, respectively, were found in 9 normal adults. Isotope-dilution assays are sensitive enough to determine tyrosine, p-hydroxyphenylpyruvate and p-hydroxyphenyllactate content in normal subjects, and may be useful for studying disorders of tyrosine metabolism, including inborn errors of metabolism, liver disease and ascorbic acid deficiencies.

Carbon Isotopes↗
PubMed1995

Interaction between the Ah receptor and proteins binding to the AP-1-like electrophile response element (EpRE) during murine phase II [Ah] battery gene expression.

We have studied three Phase II genes in the mouse dioxin-inducible [Ah] battery: Nmo1 [encoding NAD(P)H:menadione oxidoreductase], Ahd4 (encoding the cytosolic aldehyde dehydrogenase ALDH3c), and Ugt1*06 (a UDP glucuronosyltransferase). Oxidant-induced Nmo1 gene expression in the c14CoS/c14CoS mouse appears likely to be caused by homozygous loss of the fumarylacetoacetate hydrolase (Fah) gene on Chr 7 and absence of the enzyme (FAH), which leads to increased levels of endogenous tyrosine oxidative metabolites. We show here that increases in [Ah] Phase II gene expression in the 14CoS/14CoS mouse are correlated with an AP-1-like DNA motif called the electrophile response element (EpRE), which has been found in the 5' flanking regulatory regions of all murine (Ah) Phase II genes. Aromatic hydrocarbon response element (AhREs) are responsible for dioxin-mediated upregulation of all six [Ah] battery genes, and one or more AhREs have been found in the 5' flanking regulatory regions of all of these [Ah] genes. Gel mobility shift assays, with a synthetic oligonucleotide probe corresponding to the EpRE, show that EpRE-binding proteins are more than twice as abundant in 14CoS/14CoS than in the wild-type ch/ch nuclear extracts. Competition studies of EpRE-specific binding with an excess of EpRE, mutated EpRE, AP-1, AhRE3, mutated AhRE3, and C/EBP alpha oligonucleotides suggest that several common transcriptional factors bind to the EpRE and AhRE3 motifs. Two monospecific antibodies to the Ah receptor (AHR) protein block formation of an EpRE-specific complex on gel mobility electrophoresis. These data suggest that AHR (or AHR-related protein) might be an integral part of the EpRE-binding transcriptional complex associated with the oxidative stress response. To our knowledge, this is among the first reports of the same transcription factor operating at two different response elements upstream of a single gene.

Aldehyde Dehydrogenase↗
PubMed1993

Threonine 246 at the active site of the L-lactate dehydrogenase of Bacillus stearothermophilus is important for catalysis but not for substrate binding.

Threonine 246 is an active site residue that is conserved in all known L-lactate dehydrogenase (LDH; EC 1.1.1.27) sequences. In order to investigate the role of Thr246 in Bacillus stearothermophilus LDH, this residue was altered by site-directed mutagenesis to valine, alanine, leucine, and serine, respectively. The effects of these mutations, as observed in both steady-state and single-turnover kinetic measurements with different substrates, demonstrated the importance for catalysis of a hydroxyl group in the 246 amino acid residue. In contrast, no significant contribution of the OH group of Thr246 to productive pyruvate binding was observed. Instead, it is proposed that the role of Thr246 may be to facilitate hydride transfer from the nicotinamide ring of the NADH cofactor to the pyruvate carbonyl group.

Base Sequence↗
PubMed1976

Lethality of tyrosine in mice: its potentiation by decarboxylase inhibitors and reversal byascorbic acid.

High doses of tyrosine were found to be lethal in mice. The lethality was potentiated by decarboxylase inhibitors which acted by elevating tissues tyrosine levels when given together with large amounts of tyrosine. The lethality of either tyrosine or tyrosine given in combination with decarboxylase inhibitors was found to be correlated with the elevation of tyrosine levels in liver. This toxicity does not appear to involve either tyramine or p-hydroxyphenylpyruvic acid formation. Ascorbic acid pretreatment afforded a marked protection against tyrosine toxicity. This compound was found to prevent the elevation of tissue tyrosine levels by stimulating p-hydroxyphenylpyruvic acid oxidase, increasing the urinary excretion and inhibiting the gastrointestinal absorption of tyrosine.

Animals↗
PubMed2004

4-Hydroxyphenylpyruvate dioxygenase: a hybrid density functional study of the catalytic reaction mechanism.

Density functional calculations using the B3LYP functional has been used to study the reaction mechanism of 4-hydroxyphenylpyruvate dioxygenase. The first part of the catalytic reaction, dioxygen activation, is found to have the same mechanism as in alpha-ketoglutarate-dependent enzymes; the ternary enzyme-substrate-dioxygen complex is first decarboxylated to the iron(II)-peracid intermediate, followed by heterolytic cleavage of the O-O bond yielding an iron(IV)-oxo species. This highly reactive intermediate attacks the aromatic ring at the C1 position and forms a radical sigma complex, which can either form an arene oxide or undergo a C1-C2 side-chain migration. The arene oxide is found to have no catalytic relevance. The side-chain migration is a two-step process; the carbon-carbon bond cleavage first affords a biradical intermediate, followed by a decay of this species forming the new C-C bond. The ketone intermediate formed by a 1,2 shift of an acetic acid group rearomatizes either at the active site of the enzyme or in solution. The hypothetical oxidation of the aromatic ring at the C2 position was also studied to shed light on the 4-HPPD product specificity. In addition, the benzylic hydroxylation reaction, catalyzed by 4-hydroxymandelate synthase, was also studied. The results are in good agreement with the experimental findings.

4-Hydroxyphenylpyruvate Dioxygenase↗
PubMed1981

[Diaplacental influence on the disseminated intravascular coagulation (DIC) in an asphyxia model. II. Influence on the vessel's content (author's transl)].

There is reported on the possibilities of diaplacental influencing on the DIC arising from the hypoxia we provoked with the help of an asphyxia model in rabbit fetuses. We could demonstrate the impossibility of influencing on the fetal vasal content by means of low molecular dextran, heparin or streptokinase. On the contrary, the possibility exists to influence on the fetal hemostasis by low molecular synthetic substances. The antifibrinolytic drug PAMBA causes in case of advanced acidosis diaplacental a definite growth of the intravascular coagulation, as well. But an inhibition of the fibrin sedimentation in the terminal vessels at the asphyctic shock can be achieved by applying the ethyl ester of the 4-amidinophenylpyruvic acid (APPA).

4-Aminobenzoic Acid↗