Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0031511 (pheochromocytoma)
14,622 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new procedure that permits large-scale purification of tyrosine 3-monooxygenase (tyrosine hydroxylase) (L-tyrosine,tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2) from the cytosolic fraction of bovine adrenal medulla is described. The homogenous enzyme revealed a subunit Mr of 60,000 and a specific activity of 425 nmol.min-1.mg-1. The N-terminal amino-acid sequence (27 residues) revealed 89% homology with the human pheochromocytoma enzyme as deduced from its cDNA sequence. The pure enzyme contained 0.66 +/- 0.09 mol iron, 0.13 mol zinc and 0.62 +/- 0.04 mol phosphate per mol subunit of Mr = 60,000. A broad light absorption band with its maximum around 700 nm (epsilon 700 nm = 1.3 (mM monomer)-1.cm-1) explains its blue-green color. EPR spectra at 3.6 K revealed high-spin Fe(III) (S = 5/2) in an environment of nearly axial symmetry (g values at 7.2-6.7, 4.7-5.3 and 1.9-2.0). A close correlation was observed between the absorbance at 700 nm and the intensity of the axial type of EPR spectrum. The absorption peak at 700 nm is compatible with a ligand-to-iron charge-transfer transition as a result of catecholate coordination to the iron. Physicochemical studies suggest that the enzyme does not undergo such major substrate- or cofactor-induced conformational changes as have been reported for the related enzyme, phenylalanine hydroxylase.
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PMID:Soluble tyrosine hydroxylase (tyrosine 3-monooxygenase) from bovine adrenal medulla: large-scale purification and physicochemical properties. 289 60

The survival and functional properties of dispersed cell implants of catecholaminergic cells obtained from the peripheral nervous system of adult rats (adrenal medulla and carotid body glomus cells) and PC12 cells from a rat pheochromocytoma cell line were examined following transplantation into the striatum of the adult rat. The host animals, all with unilateral 6-hydroxydopamine (6-OHDA) nigrostriatal lesions, were divided into 5 groups: (1) PC12 cells transplanted into Cyclosporin-A treated hosts; (2) PC12 cell grafts into hosts without Cyclosporin-A treatment; (3) grafts of adrenal medullary cells; (4) grafts of glomus cells; and (5) vehicle controls. All animals were sacrificed one month after transplantation. Immunocytochemical staining for tyrosine hydroxylase, the rate-limiting enzyme for catecholamine synthesis, was used to identify and characterize the grafted cells. PC12 cells were detected in four of six Cyclosporin-A treated rats, and two of these grafts developed into tumors. However, only one of the six non-Cyclosporin-A treated hosts was found to have surviving PC12 cells, and none of these rats developed tumors. No significant differences in rotational behavior were seen in either of the PC12 cell recipient groups. Grafted cells could be identified in all of the adrenal medullary and glomus cell recipients. However, the number of surviving cells was quite limited, with not more than 100 tyrosine hydroxylase-positive grafted cells found in any one recipient. Tyrosine hydroxylase-positive fibers were present adjacent to the transplants in these latter graft recipients, but the fibers appeared to be of host origin rather than from the grafts.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparison of adrenal medullary, carotid body and PC12 cell grafts in 6-OHDA lesioned rats. 289 33

Stimulation of rat pheochromocytoma PC12 cells with ionophore A23187, carbachol, or high K+ medium, agents which increase intracellular Ca2+, results in the phosphorylation and activation of tyrosine hydroxylase (Nose, P., Griffith, L. C., and Schulman, H. (1985) J. Cell Biol. 101, 1182-1190). We have identified three major protein kinases in PC12 cells and investigated their roles in the Ca2+-dependent phosphorylation of tyrosine hydroxylase and other cytosolic proteins. A set of PC12 proteins were phosphorylated in response to both elevation of intracellular Ca2+ and to protein kinase C (Ca2+/phospholipid-dependent protein kinase) activators. In addition, distinct sets of proteins responded to either one or the other stimulus. The three major regulatory kinases, the multifunctional Ca2+/calmodulin-dependent protein kinase, the cAMP-dependent protein kinase, and protein kinase C all phosphorylate tyrosine hydroxylase in vitro. Neither the agents which increase Ca2+ nor the agents which directly activate kinase C (12-O-tetradecanoylphorbol-13-acetate or 1-oleyl-2-acetylglycerol) increase cAMP or activate the cAMP-dependent protein kinase, thereby excluding this pathway as a mediator of these stimuli. The role of protein kinase C was assessed by long term treatment of PC12 cells with 12-O-tetradecanoylphorbol-13-acetate, which causes its "desensitization." In cells pretreated in this manner, agents which increase Ca2+ influx continue to stimulate tyrosine hydroxylase phosphorylation maximally, while protein kinase C activators are completely ineffective. Comparison of tryptic peptide maps of tyrosine hydroxylase phosphorylated by the three protein kinases in vitro with phosphopeptide maps generated from tyrosine hydroxylase phosphorylated in vivo indicates that phosphorylation by the Ca2+/calmodulin-dependent kinase most closely mirrors the in vivo phosphorylation pattern. These results indicate that the multifunctional Ca2+/calmodulin-dependent protein kinase mediates phosphorylation of tyrosine hydroxylase by hormonal and electrical stimuli which elevate intracellular Ca2+ in PC12 cells.
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PMID:The multifunctional Ca2+/calmodulin-dependent protein kinase mediates Ca2+-dependent phosphorylation of tyrosine hydroxylase. 289 67

Activation of rat pheochromocytoma tyrosine hydroxylase by limited tryptic proteolysis was investigated. The modifications produced upon the enzyme's structure were analyzed with the use of sodium dodecyl sulfate/polyacrylamide gel electrophoresis and tyrosine hydroxylase activity was measured all through the digestion. During the proteolysis the activity of tyrosine hydroxylase was elevated threefold at the same time as a 56-kDa tryptic fragment was formed. When the enzyme was phosphorylated, at its N-terminal region, by a kinase copurified with tyrosine hydroxylase, the major 56-kDa species did not appear to be phosphorylated on the autoradiograph, suggesting that it was derived from the native subunit by cleavage of the N-terminal of the protein. The reactivity of the 2/40/15 anti-(tyrosine hydroxylase) monoclonal antibody with the N-terminal of tyrosine hydroxylase was also investigated, using the Western-blot technique. This antibody reacted with the 62-kDa hydroxylase subunit but not with the 60-kDa tryptic fragment; the amino acid sequences of these two species showed that the 60-kDa fragment lacked the first 16 N-terminal amino acids of the native molecule. These results suggest that the N-terminal region of tyrosine hydroxylase is apparently responsible for an inhibition of the hydroxylase activity and that the first N-terminal amino acids of the hydroxylase are necessary for the recognition of the enzyme by its antibody.
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PMID:Role of the N-terminus of rat pheochromocytoma tyrosine hydroxylase in the regulation of the enzyme's activity. 289 26

Effects of the 1-methyl-4-phenylpyridinium ion (MPP+) on DOPA formation and phosphorylation of tyrosine hydroxylase (TH) of rat pheochromocytoma PC12h cells were examined after the cells were cultured with MPP+. DOPA formed from endogenous tyrosine in PC12h cells after a 3-day culture with 100 microM MPP+ was decreased to less than 50% as compared to that in the control cells cultured without MPP+. Kinetical study showed that two apparent forms of TH with different Km existed in the cells cultured with 100 microM MPP+ but one form in that of control. Incorporation of radioactive phosphate into TH molecule was also reduced to 50% of its control value following a 3-day exposure to 100 microM MPP+. These results suggest that MPP+ acutely inhibits the phosphorylation of TH to decrease cellular DOPA formation.
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PMID:Effect of the 1-methyl-4-phenylpyridinium ion on phosphorylation of tyrosine hydroxylase in rat pheochromocytoma PC12h cells. 289 10

A simple assay procedure for tyrosine hydroxylase activity in crude tissue samples was devised that requires minimal sample preparation and use of high-performance liquid chromatography with coulometric electrochemical detection. After incubation of enzyme samples, such as human brain homogenates or rat pheochromocytoma PC12h cells, with L-tyrosine and a tetrahydropterin cofactor, in the presence or absence of p-bromobenzyloxyamine, an inhibitor of aromatic L-amino acid decarboxylase, the reaction was terminated by addition of an equal volume of 0.1 M perchloric acid. For quantitation of L-DOPA produced, the sample was centrifuged, filtered and directly applied to the chromatographic apparatus connected to a coulometric electrochemical detector. This method makes redundant a time-consuming step in the previous methods, purification and concentration of L-DOPA or dopamine using alumina. The reaction conditions for the assay of tyrosine hydroxylase activity in brain homogenates and PC12h cells were re-examined by this method. Both tyrosine hydroxylase samples required a naturally occurring cofactor, (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin [(6R)BH4], catalase and NSD-1055 for the full activity, and tyrosine hydroxylase in human brain homogenates required Fe2+ ions for its full activity. (6R)BH4 proved to be a more effective cofactor than a synthetic cofactor, (6RS)-methyl-5,6,7,8-tetrahydropterin, which is commonly used for this assay.
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PMID:Simple assay procedure for tyrosine hydroxylase activity by high-performance liquid chromatography employing coulometric detection with minimal sample preparation. 290 Aug 41

Tyrosine hydroxylase activity is reversibly modulated by the actions of a number of protein kinases and phosphoprotein phosphatases. A previous report from this laboratory showed that low-molecular-weight substances present in striatal extracts lead to an irreversible loss of tyrosine hydroxylase activity under cyclic AMP-dependent phosphorylation conditions. We report here that ascorbate is one agent that inactivates striatal tyrosine hydroxylase activity with an EC50 of 5.9 microM under phosphorylating conditions. Much higher concentrations (100 mM) fail to inactivate the enzyme under nonphosphorylating conditions. Isoascorbate (EC50, 11 microM) and dehydroascorbate (EC50, 970 microM) also inactivated tyrosine hydroxylase under phosphorylating but not under nonphosphorylating conditions. In contrast, ascorbate sulfate was inactive under phosphorylating conditions at concentrations up to 100 mM. Since the reduced compounds generate several reactive species in the presence of oxygen, the possible protecting effects of catalase, peroxidase, and superoxide dismutase were examined. None of these three enzymes, however, afforded any protection against inactivation. We also examined the effects of ascorbate and its congeners on the activity of tyrosine hydroxylase purified to near homogeneity from a rat pheochromocytoma. This purified enzyme was also inactivated by the same agents that inactivated the impure corpus striatal enzyme. Under conditions in which ascorbate almost completely abolished enzyme activity, we found no indication for significant proteolysis of the purified enzyme as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We also found that pretreatment of PC12 cells in culture for 4 h with 1 mM ascorbate, dehydroascorbate, or isoascorbate (but not ascorbate sulfate) also decreased tyrosine hydroxylase activity 25-50%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inactivation of tyrosine hydroxylase activity by ascorbate in vitro and in rat PC12 cells. 290 63

1-Methyl-4-phenylpyridinium ion (MPP+), a metabolite of a neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, was found to reduce dopamine (DA) level and the activity of enzymes related to its metabolism in clonal rat pheochromocytoma PC12h cells. After 6 days' culture in the presence of 1 mM and 100 microM MPP+, DA content in PC12h cells was reduced markedly, but with MPP+ at concentrations lower than 10 microM, DA levels in the cells did not change. The amounts of 3,4-dihydrophenylacetic acid (DOPAC), a metabolite of DA were reduced markedly in culture medium and in PC12h cells cultured with MPP+ at concentrations higher than 1 microM. MPP+ was found to reduce the enzyme activity of tyrosine hydroxylase (TH), monoamine oxidase (MAO) and aromatic L-aminoacid decarboxylase (AADC). In the presence of MPP+ at concentrations higher than 10 microM, reduction of TH activity in the cells was more pronounced than reduction of cell protein or of the activity of a non-specific enzyme, beta-galactosidase. With 1 mM and 100 microM MPP+, MAO activity was reduced to about 30% of that in control cells. Reduction was observed with MPP+ at concentrations higher than 1 microM. AADC was the most sensitive to MPP+ and its activity was reduced markedly in the cells cultured with 100 nM MPP+. These results indicate that MPP+ inhibits not only the biosynthesis of catecholamines, but also the enzyme participating in their catabolism in cells, and may thus perturb catecholamine levels in the brain.
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PMID:Effect of 1-methyl-4-phenylpyridinium ion (MPP+) on catecholamine levels and activity of related enzymes in clonal rat pheochromocytoma PC12h cells. 290 26

The tissue contents of catecholamine, its precursor and its major metabolites were determined in 8 human pheochromocytomas and 26 normal adrenal glands. Pheochromocytomas contained significantly larger amounts of norepinephrine, dopamine, dihydroxyphenylalanine, tyrosine hydroxylase activity, metanephrine, normetanephrine and vanillylmandelic acid than did normal adrenal medullae. The content ratio of epinephrine/norepinephrine in normal adrenal medullae was significantly higher than that in pheochromocytomas but there were considerable individual variations in the metanephrine/normetanephrine and vanillylmandelic acid/3-methoxy-4-hydroxyphenylethylglycol ratios in pheochromocytomas. In normal adrenal medullae the tissue content of tyrosine hydroxylase activity correlated inversely with the tissue contents of epinephrine (r equals -0.78, p less than 0.001), norepinephrine (r equals -0.78, p less than 0.001) and total catecholamines (r equals -0.87, p less than 0.001), respectively but no significant relation was found between both parameters in pheochromocytomas. These results indicate the possible presence of a negative feedback mechanism of catecholamine via tyrosine hydroxylase in normal adrenal medullae but none in pheochromocytomas. In addition, the increased degradation catecholamine pathway in pheochromocytomas appears to be unstable compared to that in normal adrenal medullae.
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PMID:Catecholamine metabolism in pheochromocytoma and normal adrenal medullae. 290 37

Out of carcinogenic heterocyclic amines, which are produced by pyrolysis of tryptophan in food, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) were found to reduce the activity of enzymes related to catecholamine metabolism in clonal rat pheochromocytoma PC12h cells. By 6 days' culture in the presence of 10 nM to 10 microM Typ-P-1 and -2, these heterocyclic amines were accumulated in the cells, and activity of tyrosine hydroxylase (TH) and aromatic L-aminoacid decarboxylase (AADC) were reduced markedly. Reduction of these enzyme activity was observed with Trp-P-1 and -2 at the concentrations lower than 1 microM, while cell protein and enzyme activity of a non-specific enzyme, beta-galactosidase were reduced only with 10 microM Trp-P-1. These results show that these heterocyclic amines are neurotoxins specific for dopaminergic neurons.
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PMID:Reduction of enzyme activity of tyrosine hydroxylase and aromatic L-aminoacid decarboxylase in clonal pheochromocytoma PC12h cells by carcinogenic heterocyclic amines. 290 12


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