Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.11 (AMPK)
 12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The tyrosine-3-monooxygenase activity [L-tyrosine, tetrahydropteridine: oxygen oxidoreductase (3-hydroxylating); EC 1.14.16.2] of rat adrenal medulla is induced 20-24 hr after the injection of reserpine (16 mumol/kg intraperitoneally). This and other inducing stimuli increase the 3': 5'-cyclic AMP (cAMP) content in the medulla for longer than 60 min and activate the cAMP-dependent protein kinase (ATP: protein phosphotransferase; EC 2.7.1.37) for several hours. Corticotropin (ACTH), dopamine, and propranolol do not induce the monooxygenase, but elicit an increase in the cAMP content of the medulla which fails to activate protein kinase and lasts less than 1 hr. A high- and low-molecular-weight protein kinase are separated by gel filtration from the 20,000 X g pellet extract of adrenal medulla homogenate. The activity of the low-molecular-weight enzyme is expressed as its ability to phosphorylate histone. The protein kinase activity of the pellet is increased between 3 and 17 hr after reserpine injection. Our evidence indicates that this increase is due to a translocation from cytosol to subcellular structures of a kinase that utilizes lysine-rich histone as phosphate acceptor. The protein kinase activity that is extracted from a purified nuclear fraction prepared from the adrenal medulla of rats injected 7 hr previously with reserpine is greater than that extracted from medulla of saline-treated rats.
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PMID:Activation and nuclear translocation of protein kinase during transsynaptic induction of tyrosine 3-monooxygenase. 0 93

An increase of cAMP/cGMP concentration ratio is the earliest stimulus-coupled biochemical change that has been measured in the adrenal medulla during the trans-synaptic induction of tyrosine 3-monooxygenase [EC 1.14.16.2; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating)]. In adrenal medulla of rats receiving reserpine alone (16 mumol/kg intraperitoneally) or reserpine and propranolol (40 mumol/kg intraperitoneally 30 min before reserpine), or exposed to 4 degrees for 4 hr, the extent and duration of the increase of the cAMP/cGMP concentration ratio exceeds the critical value that is required to activate the protein kinases (EC 2.7.1.37; ATP:protein phosphotransferase). Gel filtration experiments indicate that during this activation, the catalytic subunit of the protein kinase (low-molecular-weight enzyme) is released from the holoenzyme. The activation of protein kinase lasts longer than the increase in the cAMP/cGMP concentration ratio and appears to be an obligatory early event that mediates the increase of tyrosine monooxygenase synthesis. The trans-synaptic induction of the monooxygenase in adrenal medulla appears to be due to an increased synthesis of the enzyme;the rate for monooxygenase degradation is proportional to the number of enzyme molecules that are present at various stages of the induction process.
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PMID:Protein kinase activation as an early event in the trans-synaptic induction of tyrosine 3-monooxygenase in adrenal medulla. 23 57

Recombinant rat PC12 tyrosine hydroxylase, also called tyrosine 3-monooxygenase [L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2], purified from Escherichia coli is in an activated form with a low Km for the tetrahydrobiopterin cofactor and a pH optimum of 6.5. Pretreatment with low levels of the derived product, dopamine, inhibits catalytic activity, increases the Km for the cofactor, and shifts the pH curve towards a more acidic pH optimum. Labeled dopamine binds to tyrosine hydroxylase with high affinity (Kd = 1 microM) but low stoichiometry (r = 0.08 mol/mol of enzyme subunit). The binding of dopamine results in the appearance of a blue-green chromophore with lambda max at approximately 660 nm, which is consistent with the formation of a catecholamine-iron complex. In the absence of dopamine, the recombinant enzyme cannot be further activated by phosphorylation with cAMP-dependent protein kinase, although as much as 1 mol of phosphate is incorporated per mol of subunit. In contrast, the enzyme pretreated with dopamine is activated by phosphorylation in the same fashion and to the same extent as the native hydroxylase. The results suggest that the high-affinity binding of catecholamine products is a pivotal post-translational modification that determines the state of enzyme activation and the response to phosphorylation.
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PMID:Regulation of recombinant rat tyrosine hydroxylase by dopamine. 135 65

Activation of rat striatal tyrosine hydroxylase [TyrOHase; tyrosine monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] by ATP/Mg2+ and endogenous protein kinase can be produced without the addition of cAMP. This activation is not due to endogenous free catalytic subunit derived from cAMP-dependent protein kinase. In the presence of amounts of protein kinase inhibitor sufficient for complete inhibition of striatal cAMP-dependent protein kinase and the cAMP-mediated activation of TyrOHase, addition of ATP/Mg2+ results in an enhancement of TyrOHase activity. Enzyme activation does not occur when the nonhydrolyzable form of ATP, adenylyl imidodiphosphate, is substituted for ATP. When TyrOHase is assayed in the presence of ATP/Mg2+ and different concentrations of either tyrosine or 6-methyltetrahydropterin co-factor, a 2-fold increase in enzyme Vmax is demonstrable, with no change in the Km for either substrate or cofactor. In contrast, in the presence of cAMP and ATP/Mg2+, both an increase in Vmax and an enhanced affinity for pterin cofactor are demonstrable. In the latter circumstance, the 2-fold increase in Vmax can be attributed entirely to the action of cAMP-independent protein kinase. The addition of either EGTA or CaCl2 does not modify the effect seen in the presence of ATP, suggesting that the effect of ATP/Mg2+ is not mediated by a Ca2+-dependent protein kinase. These data support the existence of a cAMP-independent striatal protein kinase that can catalyze the activation of TyrOHase.
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PMID:Evidence for the involvement of a cyclic AMP-independent protein kinase in the activation of soluble tyrosine hydroxylase from rat striatum. 613 85

(R)-N6-Phenylisopropyladenosine (PIA) stimulates dopa production 3- to 5-fold in PC12 cells, with a half-maximal effective concentration (EC50) of 50 nM. This increase can be explained by a stable activation of tyrosine hydroxylase [TyrOHase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] when it is phosphorylated by a cAMP-dependent protein kinase. The activation of TyrOHase is mediated by the adenosine-dependent activation of adenylate cyclase (EC50 = 600 nM). PIA (10 microM) is as effective as cholera toxin or dibutyryl cAMP in activating TyrOHase in wild-type cells. Adenosine kinase-deficient mutants of PC12 were found to be resistant to PIA-dependent activation of TyrOHase (EC50 = 100-1000 nM). This phenomenon was explored in detail in one adenosine kinase-deficient mutant and was shown to occur because the mutant was resistant to the adenosine-dependent activation of adenylate cyclase. In this mutant, TyrOHase was activated 14-fold by cholera toxin, suggesting that activated TyrOHase is about 14 times as active as unactivated TyrOHase. These studies with kinase-deficient PC12 cells provide genetic evidence that adenosine-dependent activation of TyrOHase is mediated by acute increases in cAMP. When the adenosine receptor found on PC12 cells is expressed in vivo, it might function as either a presynaptic (i.e., localized on the nerve terminal) or a postsynaptic (i.e., localized on the cell body or dendrite) receptor that regulates rates of transmitter synthesis in response to cell activity.
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PMID:Adenosine-dependent activation of tyrosine hydroxylase is defective in adenosine kinase-deficient PC12 cells. 614 82

Tyrosine hydroxylase (TH) catalyzes the conversion of L-tyrosine to 3,4-dihydroxy-L-phenylalanine, the first and rate-limiting step in catecholamine biosynthesis. The cAMP-dependent protein kinase (PKA) phosphorylates and activates the TH enzyme and is thought to mediate transcriptional induction of the TH gene. To better understand the functional role of PKA in TH gene regulation, we studied TH gene expression at the transcriptional, translational, and post-translational levels in several PKA-deficient cell lines derived from rat PC12 pheochromocytoma cells. Strikingly, all PKA-deficient cell lines analyzed in this study showed substantial deficits in basal TH expression as measured by TH enzymatic activity, level of TH immunoreactivity, TH protein level, and steady-state mRNA level. Interestingly, the steady-state level of mRNA correlated well with levels of TH activity, immunoreactivity, and protein. In addition, PKA-deficient cell lines lacked transcriptional induction of the TH gene following treatment with dibutyryl cAMP. Cotransfection of PKA-deficient cells with an expression plasmid for the catalytic subunit of PKA fully reversed transcriptional defect, as indicated by robust transcriptional induction of a reporter construct containing 2400 bp of TH upstream sequence in all PC12 cells tested. These data indicate that the PKA system regulates both the basal and the cAMP-inducible expression of the TH gene primarily at the transcriptional level in PC12 cells.
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PMID:A dual role for the cAMP-dependent protein kinase in tyrosine hydroxylase gene expression. 768 5

The conversion of L-tyrosine to 3,4-dihydroxy-L-phenylalanine by tyrosine hydroxylase (TH) is the first and rate-limiting step in biosynthesis of catecholamine neurotransmitters. TH gene expression is regulated in a cell type-specific and cAMP-dependent manner. Evidence from this laboratory and others indicates that the cAMP response element (CRE), residing at -45 to -38 bp upstream of the transcription initiation site, is essential for both basal and cAMP-inducible transcription of the TH gene. To understand the control mechanisms of TH gene transcription in greater detail, we sought to identify and characterize the transcription factors involved in recognition and activation of the CRE of the TH gene. Remarkably, electrophoretic mobility shift assay and antibody supershift experiments indicated that all three major CRE-binding protein factors, i.e. CREB, ATF1, and CREM, may participate in forming specific DNA/protein complexes with the CRE of the TH gene. To address the transcriptional activation function of individual factors, we replaced the TH CRE with a GAL4-binding site and cotransfected this modified TH promoter-reporter gene with an effector plasmid that encodes GAL4-fused transcription factor. Our results indicate that CREB but not ATF1 can support basal promoter activity while both can robustly induce the promoter activity in response to co-expression of the catalytic subunit of cAMP-dependent protein kinase (PKA). We further show that the coactivator CBP up-regulates PKA-mediated activation of the TH promoter and, if tethered to the TH promoter by a GAL4-fusion, can robustly transactivate the TH promoter even in the absence of PKA. Collectively, our results suggest that multiple CRE-binding factors interact with the CRE and regulate, in conjunction with the coactivator CBP, the transcriptional activity of the TH gene.
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PMID:Regulation of tyrosine hydroxylase gene transcription by the cAMP-signaling pathway: involvement of multiple transcription factors. 1110 36

TH (tyrosine hydroxylase) is the rate-limiting enzyme in the synthesis of catecholamines. The cat-2 gene of the nematode Caenorhabditis elegans is expressed in mechanosensory dopaminergic neurons and has been proposed to encode a putative TH. In the present paper, we report the cloning of C. elegans full-length cat-2 cDNA and a detailed biochemical characterization of the encoded CAT-2 protein. Similar to other THs, C. elegans CAT-2 is composed of an N-terminal regulatory domain followed by a catalytic domain and a C-terminal oligomerization domain and shows high substrate specificity for L-tyrosine. Like hTH (human TH), CAT-2 is tetrameric and is phosphorylated at Ser35 (equivalent to Ser40 in hTH) by PKA (cAMP-dependent protein kinase). However, CAT-2 is devoid of characteristic regulatory mechanisms present in hTH, such as negative co-operativity for the cofactor, substrate inhibition or feedback inhibition exerted by catecholamines, end-products of the pathway. Thus TH activity in C. elegans displays a weaker regulation in comparison with the human orthologue, resembling a constitutively active enzyme. Overall, our data suggest that the intricate regulation characteristic of mammalian TH might have evolved from more simple models to adjust to the increasing complexity of the higher eukaryotes neuroendocrine systems.
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PMID:Divergence in enzyme regulation between Caenorhabditis elegans and human tyrosine hydroxylase, the key enzyme in the synthesis of dopamine. 2108 8