Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.14.16.2 (tyrosine hydroxylase)
 14,760 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bovine adrenal tyrosine hydroxylase has been obtained in a form that is 85 to 90% pure. Sodium dodecyl sulfate-gel electrophoresis and density gradient centrifugation studies have established that the subunit molecular weight of the chymotrypsin-solubilized enzyme is 34,000. The presence of iron in the purified enzyme (0.50 to 0.75 mol of iron/mol of enzyme) has been established. Crude particulate tyrosine hydroxylase can be activated by the phospholipid, phosphatidyl-L-serine, or by exposure to enzymatic phosphorylating conditions. Both forms of activation lower the Km of the enzyme for its 2-amino-4-hydroxypteridine cofactor. By contrast, tyrosine hydroxylase that has been solubilized by chymotrypsin cannot be activated by either of these methods.
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PMID:Bovine adrenal tyrosine hydroxylase: purification and properties. 1 85

Rat tyrosine hydroxylase expressed with a baculovirus expression system contains covalent phosphate and has kinetic parameters consistent with those expected of phosphorylated enzyme (Fitzpatrick, P. F., Chlumsky, L. J., Daubner, S. C., and O'Malley, K. L. (1990) J. Biol. Chem. 265, 2042-2047). The phosphorylation site was identified as serine 40, by purifying the enzyme from cells grown in the presence of [32P]phosphate. Replacement of serine 40 with alanine by site-directed mutagenesis prevented phosphorylation but had little effect on the steady-state kinetic parameters at pH 7. Both wild type and S40A tyrosine hydroxylase were expressed in Escherichia coli; the kinetic parameters of the enzymes purified from bacteria were nearly identical to those of the enzymes expressed with the baculovirus system, although the bacterially expressed enzyme contained no covalent phosphate. Treatment of this wild type enzyme with cAMP-dependent protein kinase decreased the KBH4 value about 2-fold but had no effect on the Vmax value at pH 7. Treatment with a stoichiometric amount of dopamine decreased the Vmax value 15-fold and increased the KBH4 value 2-3-fold. Phosphorylation of the dopamine-bound enzyme increased the Vmax value 10-fold and decreased the KBH4 value 2-fold. The kinetic parameters of the dopamine-bound recombinant enzyme were identical to those of enzyme purified from PC12 cells. In contrast, the S40A enzyme was converted to a less active form by treatment with dopamine but was not affected by phosphorylating conditions. These results are consistent with a model in which the major effect of phosphorylation of serine 40 is to relieve tyrosine hydroxylase from the inhibitory effects of catecholamines.
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PMID:Site-directed mutagenesis of serine 40 of rat tyrosine hydroxylase. Effects of dopamine and cAMP-dependent phosphorylation on enzyme activity. 135 89

We have investigated the role of serine 40 (Ser-40) in tyrosine hydroxylase (TH) catalysis of basal and activated enzymes by protein kinase A (PKA)-mediated phosphorylation. Wild type and mutant TH were transiently and stably expressed in AtT-20 cells, and the enzymatic activities of the recombinant enzymes were analyzed. The specific enzymatic activity of transiently expressed TH mutants Ser-40-->leucine or-->tyrosine (Leu-40m or Tyr-40m) was higher than that of the wild type enzyme or of other mutants in which Ser-8, -19, and -31 were replaced by leucine. The kinetic studies carried out with the stably expressed TH show that the Km for the cofactor 6-methyltetrahydropterine is lower and the Ki for dopamine is higher when the enzymatic hydroxylation is catalyzed by the Leu-40m or Tyr-40m than by the wild type enzyme. The kinetic parameters and the pH profile of the enzymatic hydroxylation catalyzed by the Leu-40m or Tyr-40m are similar to the enzyme activated by PKA-mediated phosphorylation. We suggest that Ser-40 in TH exerts an inhibitory influence on the enzymatic activity, and its replacement with another amino acid by site-directed mutagenesis or its modification by phosphorylation leads to a change in conformation with an increased enzymatic activity. The importance of Ser-40 in the activation of TH by PKA-mediated phosphorylation was investigated by comparing the activation of the wild type enzyme with that of Leu-40m or Tyr-40m. The findings that the enzymatic activity is increased by PKA-mediated phosphorylation of the wild type enzyme, but not of the Leu-40m or Tyr-40m, demonstrate that phosphorylation at Ser-40 is essential for activation of TH by PKA. The findings that addition of ATP plus cAMP to homogenates from transfected AtT-20 cells stimulates the recombinant wild type TH activity indicate that these cells contain endogenous cAMP-dependent protein kinase.
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PMID:Site-directed mutagenesis of tyrosine hydroxylase. Role of serine 40 in catalysis. 136 Nov 89

The enzyme tyrosine hydroxylase catalyzes the first step in the biosynthesis of dopamine, norepinephrine, and epinephrine. Tyrosine hydroxylase is a substrate for cyclic AMP-dependent protein kinase as well as other protein kinases. We determined the Km and Vmax of rat pheochromocytoma tyrosine hydroxylase for cyclic AMP-dependent protein kinase and obtained values of 136 microM and 7.1 mumol/min/mg of catalytic subunit, respectively. These values were not appreciably affected by the substrates for tyrosine hydroxylase (tyrosine and tetrahydrobiopterin) or by feedback inhibitors (dopamine and norepinephrine). The high Km of tyrosine hydroxylase correlates with the high content of tyrosine hydroxylase in catecholaminergic cells. We also determined the kinetic constants for peptides modeled after actual or potential tyrosine hydroxylase phosphorylation sites. We found that the best substrates for cyclic AMP-dependent protein kinase were those peptides corresponding to serine 40. Tyrosine hydroxylase (36-46), for example, exhibited a Km of 108 microM and a Vmax of 6.93 mumol/min/mg of catalytic subunit. The next best substrate was the peptide corresponding to serine 153. The peptide containing the sequence conforming to serine 19 was a very poor substrate, and that conforming to serine 172 was not phosphorylated to any significant extent. The primary structure of the actual or potential phosphorylation sites is sufficient to explain the substrate behavior of the native enzyme.
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PMID:Phosphorylation of rat tyrosine hydroxylase and its model peptides in vitro by cyclic AMP-dependent protein kinase. 167 83

We have investigated the ability of exogenous gangliosides to modulate nerve growth factor (NGF) signal transduction in PC12 cells. The effects of exogenous ganglioside GM1 on multiple protein kinase activities were assayed by analyzing site-specific serine phosphorylation of tyrosine hydroxylase (TyrOHase) by two-dimensional phosphopeptide mapping. In the presence of NGF, exogenous GM1 (1-10 microM) increased 32P incorporation into TyrOHase phosphopeptide T2, a Ca2+/calmodulin-dependent protein kinase substrate whose phosphorylation is not normally affected by NGF treatment. In the absence of NGF, GM1 treatment had no significant effects on TyrOHase phosphorylation. The removal of extracellular Ca2+ or blockade of dihydropyridine-sensitive Ca2+ channels prevented the GM1-induced increases in 32P incorporation into phosphopeptide T2. Exogenous GM1 also potentiated K+ depolarization-induced increases in the phosphorylation of TryOHase. These results suggest that the stimulatory effects of exogenous GM1 ganglioside on NGF actions may be due to its ability to potentiate a Ca(2+)-dependent signaling pathway.
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PMID:Stimulation of a Ca(2+)-dependent protein kinase by GM1 ganglioside in nerve growth factor-treated PC12 cells. 167 13

The phosphorylation and activation of tyrosine hydroxylase was examined in PC12 cells following depolarization with KCl or treatment with nerve growth factor. Both treatments activate tyrosine hydroxylase (TH) and increase enzyme phosphorylation. Site-specific analysis of the tryptic phosphopeptides of TH isolated from [32P]phosphate-labeled PC12 cells demonstrated that the major phosphorylated peptide (termed "H25") did not contain any of the previously reported phosphorylation sites. Phosphoamino acid analysis of this peptide demonstrated that the phosphorylated residue was a serine. Synthetic tryptic peptides containing putative phosphorylation sites were prepared, and subjected to high performance liquid chromatography analysis and isoelectric focusing. The tryptic phosphopeptide containing serine 31 comigrated with the H25 peptide during both of these analytical techniques. The tryptic phosphopeptide produced by the phosphorylation of tyrosine hydroxylase by the recently discovered proline-directed protein kinase and the phosphorylated synthetic phosphopeptide TH2-12 are clearly separated from H25 by this analysis. We conclude that serine 31 is phosphorylated during KCl depolarization and nerve growth factor treatment of PC12 cells and that this phosphorylation is responsible for the activation of tyrosine hydroxylase. Since this site is not located in a sequence selective for any of the "classical" protein kinases, we suggest that a novel protein kinase may be responsible for the phosphorylation of this site. Since serine 31 has a proline residue on the carboxyl-terminal side, the possibility that this kinase may be related to the recently reported proline-directed protein kinase is discussed. Other sites that are also phosphorylated on TH during KCl depolarization include serine 19, which is known to be phosphorylated by calmodulin-dependent protein kinase II. A schematic model for the regulation of tyrosine hydroxylase activity by phosphorylation of the NH2-terminal regulatory domain is presented.
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PMID:Site-specific phosphorylation of tyrosine hydroxylase after KCl depolarization and nerve growth factor treatment of PC12 cells. 197 80

During investigations of the regulation of tyrosine hydroxylase (TH) by protein phosphorylation, a novel protein kinase activity has been discovered in rat pheochromocytoma. Originally detected as a trace contaminant in preparations of highly purified TH, this novel kinase activity phosphorylated TH at serine 8 in the proline-rich amino-terminal region of the enzyme. This particular site is not phosphorylated by, nor is the amino acid sequence surrounding this site selective for, any of the classical (i.e. well characterized) protein kinases. In this report, we describe the identification, characterization, and partial purification of this novel protein kinase. By utilizing a synthetic peptide corresponding to the amino-terminal region of TH, a selective assay for this protein kinase was developed. The kinase activity utilized ATP and magnesium, although GTP could also be utilized as a phosphate donor. The kinase activity was found to co-purify with TH activity through ammonium sulfate precipitation and DEAE-cellulose chromatography and could be only partially resolved from TH by heparin-agarose affinity chromatography. Substantial kinase activity could be resolved from TH by phosphocellulose chromatography. The novel kinase migrates as a protein with a molecular mass of approximately 45 kDa on gel permeation chromatography as well as sucrose density gradient centrifugation. Studies of site specificity indicate that this Ser/Thr kinase activity appears to be directed by an adjacent (carboxyl-terminal) proline residue, exhibiting a minimal recognition sequence of -X-Ser/Thr-Pro-X-. In addition to TH, this proline-directed protein kinase will also phosphorylate synapsin I, histone H1, and glycogen synthase, suggesting that this kinase may have multiple substrates in vivo. Additional findings indicate that the activity of proline-directed protein kinase is increased transiently in PC12 pheochromocytoma cells following treatment with nerve growth factor. Distinctions between this novel kinase and other well characterized protein kinases can be made on the basis of phosphorylation site specificity, chromatographic behavior, and physical characteristics.
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PMID:Identification of a novel proline-directed serine/threonine protein kinase in rat pheochromocytoma. 257 Jul 79

A rapid phosphorylation of tyrosine hydroxylase occurs in the PC12 nerve-like clonal cell line in response to nerve growth factor (NGF), epidermal growth factor (EGF), dibutyryl-cAMP, cholera toxin, phorbol- 12-myristate-13-acetate (PMA), or potassium depolarization in the presence of calcium ions. Complete tryptic digestion and two-dimensional peptide mapping reveals four available sites of phosphorylation in the enzyme. Phosphoamino acid analysis demonstrates that serine is the amino acid residue phosphorylated in each peptide. Specific phosphorylation of each of the four sites is achieved by different subsets of the above agents. One peptide site is phosphorylated in response to EGF alone. A second site is phosphorylated only in response to NGF, cholera toxin or dibutyryl-cAMP. A third site is phosphorylated only in response to potassium depolarization and requires the presence of extracellular Ca2+. The fourth site is the only site phosphorylated in response to PMA. These data indicate that at least 4 distinct kinase systems can act to phosphorylate tyrosine hydroxylase in PC12 cells. The PMA-stimulated peptide site is also phosphorylated in response to every one of the other agents. Further proteolytic digestions and phosphopeptide mapping of this common peptide, using Staphylococcus V8 protease and thermolysin, did not generate different phosphopeptides resulting from the different agents. These data suggest that the phosphorylation of this common peptide in response to all of the agents may be mediated by a common kinase, and, hence, that tyrosine hydroxylase phosphorylation by some agents may be mediated by two kinases. Although phosphopeptide maps of tyrosine hydroxylase resulting from cAMP elevation or NGF are qualitatively similar, quantitative differences exist, suggesting differential regulation of the same kinases by these agents. Tyrosine hydroxylase was found to be activated 2--4-fold in response to each phosphorylating agent. Thus, NGF and EGF present novel, natural means of regulating the activation state of tyrosine hydroxylase in responsive neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Nerve growth factor and other agents mediate phosphorylation and activation of tyrosine hydroxylase. A convergence of multiple kinase activities. 286 43

Incubation of rat pheochromocytoma PC12 cells with dibutyryl cyclic AMP or 56 mM K+ is associated with increased activity and enhanced phosphorylation of tyrosine hydroxylase in situ. Following incubation of the PC12 cells with 32Pi, rapid isolation of the tyrosine hydroxylase, and tryptic digestion of the enzyme, two distinct 32P-peptides can be identified after paper electrophoresis. 56 mM K+ increases 32Pi incorporation into both of these peptides, whereas dibutyryl cyclic AMP increases 32Pi incorporation into only one of these peptides. The rate of increase in the incorporation of 32Pi into these two peptides in cells treated with 56 mM K+ is similar. The phosphorylation of tyrosine hydroxylase in PC12 cells occurs exclusively on serine residues. These results suggest that tyrosine hydroxylase in PC12 cells is phosphorylated on serine residues at two or more distinct sites after 56 mM K+ -induced depolarization. Since only one of these sites is phosphorylated by cyclic AMP-dependent protein kinase, activation of tyrosine hydroxylase by 56 mM K+ may involve phosphorylation by multiple protein kinases in rat pheochromocytoma PC12 cells.
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PMID:Enhanced phosphorylation of tyrosine hydroxylase at more than one site is induced by 56 mM K+ in rat pheochromocytoma PC12 cells in culture. 286 28

Tyrosine hydroxylase, a key enzyme in the biosynthesis of catecholamines, was previously shown to be phosphorylated on four distinct serine residues in PC12 cell cultures, each one being specific for the kinase system involved (McTigue, M., Cremins, J., and Halegoua, S. (1985) J. Biol. Chem. 260, 9047-9056). A cAMP- and Ca2+-independent protein kinase was found to be associated with tyrosine hydroxylase purified from rat pheochromocytoma tumor. The use of this activity and the availability of a large amount of purified tyrosine hydroxylase allowed identification of the site phosphorylated by this kinase activity. A peptide of 1.5 kDa (about 12 residues long), carrying the phosphorylation site, was released from 32P-labeled tyrosine hydroxylase by limited proteolysis with trypsin. This peptide was isolated from trypsinized tyrosine hydroxylase by sequential gel filtration and ion exchange chromatographies. Analysis by thin layer chromatography of an acid hydrolysate of the peptide revealed that it contained phosphoserine. The sequence determination of the peptide showed that it corresponded to the residues 38-45 in the tyrosine hydroxylase primary structure (Arg-Gln-Ser(P)-Leu-Ile-Glu-Asp-Ala). Thus, the associated kinase phosphorylated Ser-40, one of the phosphorylation sites for the cAMP-dependent protein kinase also found in rat pheochromocytoma tumors. These results are compared to those recently appearing in a report by Campbell et al. (Campbell, D. G., Hardie, D. G., and Vulliet, P. R. (1986) J. Biol. Chem. 261, 10489-10492).
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PMID:Rat pheochromocytoma tyrosine hydroxylase is phosphorylated on serine 40 by an associated protein kinase. 288 82


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