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 tryptophan hydroxylase activity of the crude extract from rat brain stem was stimulated approximately 2-fold by incubation with cAMP analogues under protein phosphorylating conditions. The cAMP-dependent activation process of the enzyme needed not only cAMP-dependent protein kinase but also activator protein. The kinetic properties of the enzyme activated by cAMP-dependent protein kinase were very similar to those of the enzyme activated by calmodulin-dependent protein kinase II.
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PMID:Involvement of activator protein in the activation of tryptophan hydroxylase by cAMP-dependent protein kinase. 216 81

A full-length cDNA clone for rabbit tryptophan hydroxylase (TPH) was modified and subcloned into a bacterial expression vector. Expression of this gene in the protease-deficient strain of bacteria, BL21[DE3], produced TPH immunoreactive protein which exhibited enzyme activity. Treatment of the recombinant enzyme (in bacterial extracts) with the purified catalytic subunit of the cAMP-dependent protein kinase and [gamma-32P]-ATP resulted in specific phosphorylation of TPH. This expression system provides a means of generating and purifying large amounts of this important enzyme. Moreover, these experiments establish that TPH will serve as an in vitro substrate for cAMP-dependent protein kinase.
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PMID:Recombinant rabbit tryptophan hydroxylase is a substrate for cAMP-dependent protein kinase. 808 9

Phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase constitute a family of tetrahydropterin-dependent aromatic amino acid hydroxylases. Comparison of the amino acid sequences of these three proteins shows that the C-terminal two-thirds are homologous, while the N-terminal thirds are not. This is consistent with a model in which the C-terminal two-thirds constitute a conserved catalytic domain to which has been appended discrete regulatory domains. To test such a model, two mutant proteins have been constructed, expressed in Escherichia coli, purified, and characterized. One protein contains the first 158 amino acids of rat tyrosine hydroxylase. The second lacks the first 155 amino acid residues of this enzyme. The spectral properties of the two domains suggest that their three-dimensional structures are changed only slightly from intact tyrosine hydroxylase. The N-terminal domain mutant binds to heparin and is phosphorylated by cAMP-dependent protein kinase at the same rate as the holoenzyme but lacks any catalytic activity. The C-terminal domain mutant is fully active, with Vmax and Km values identical to the holoenzyme; these results establish that all of the catalytic residues of tyrosine hydroxylase are located in the C-terminal 330 amino acids. The results with the two mutant proteins are consistent with these two segments of tyrosine hydroxylase being two separate domains, one regulatory and one catalytic.
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PMID:Expression and characterization of catalytic and regulatory domains of rat tyrosine hydroxylase. 810 13

Rabbit brain tryptophan hydroxylase (TPH) has been expressed in insect cells (Spodoptera frugiperda) as a histidine-tagged enzyme. The specific activity of the purified fusion enzyme is 80 nmol of 5-hydroxytryptophan/min/mg. Multifunctional regulatory 14-3-3 proteins were purified from fresh bovine brain. Phosphorylation and 14-3-3 proteins play important roles in the regulation of TPH activity. We have found that phosphorylation of TPH by cAMP-dependent protein kinase increased the activity of the hydroxylase by 25-30% and that 14-3-3 proteins increased the hydroxylase activity of phosphorylated TPH by approximately 45%. Under these conditions, the 14-3-3 proteins were not phosphorylated, and unphosphorylated TPH was not activated by 14-3-3 proteins. Surface plasmon resonance analysis demonstrated that 14-3-3 proteins bind to phosphorylated TPH with an affinity constant (Ka) of 4.5 x 10(7) M-1. Binding studies using affinity chromatography also showed that 14-3-3 proteins interact with phosphorylated TPH. The dephosphorylation of TPH by protein phosphatase-1 was inhibited by 14-3-3 proteins. Our results demonstrate that 14-3-3 proteins form a complex with phosphorylated brain TPH, thereby increasing its enzymatic activity and inhibiting its dephosphorylation.
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PMID:Interaction of phosphorylated tryptophan hydroxylase with 14-3-3 proteins. 933 90

Inhibition of cAMP-dependent protein kinase (PKA) with N-[2-methylamino)ethyl]-5-isoquinolinesulfonamide (H-8) almost completely antagonized the increase in 5-HTP accumulation and 5-HIAA/5-HT ratio in hypothalamus induced by NAS-181, a 5-HT(1B) receptor antagonist, but had no effect when the mice were treated with NAS-181 together with WAY-100,635, a selective 5-HT(1A) receptor antagonist. Inhibition of Ca(2+)-calmodulin-dependent protein kinase (CaM kinase II) with the calmodulin antagonist N-(4-aminobutyl)-5-chloro-2-naphtalenesulfonamide (W-13) did not antagonise the effect of NAS-181 alone, but counteracted that evoked by the combined treatment with NAS-181 and WAY-100,635. The results indicate that activation of tryptophan hydroxylase by reducing the tone from terminal 5-HT(1B) receptors involves PKA whereas the depolarisation-induced activation of tryptophan hydroxylase involves CaM kinase II. The increase in the 5-HIAA/5-HT ratio may under the experimental conditions used suggest CaM kinase II-induced phosphorylation of synapsin I resulting in increased 5-HT release.
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PMID:Evidence for involvement of protein kinases in the regulation of serotonin synthesis and turnover in the mouse brain in vivo. 1245 32

Annotation of the sequenced Drosophila genome suggested the presence of an additional enzyme with extensive homology to mammalian tryptophan hydroxylase, which we have termed DTRH. In this work, we show that enzymatic analyses of the putative DTRH enzyme expressed in Escherichia coli confirm that it acts as a tryptophan hydroxylase but can also hydroxylate phenylalanine, in vitro. Building upon the knowledge gained from the work in mice and zebrafish, it is possible to hypothesize that DTRH may be primarily neuronal in function and expression, and DTPH, which has been previously shown to have phenylalanine hydroxylation as its primary role, may be the peripheral tryptophan hydroxylase in Drosophila. The experiments presented in this report also show that DTRH is similar to DTPH in that it exhibits differential hydroxylase activity based on substrate. When DTRH uses tryptophan as a substrate, substrate inhibition, catecholamine inhibition, and decreased tryptophan hydroxylase activity in the presence of serotonin synthesis inhibitors are observed. When DTRH uses phenylalanine as a substrate, end product inhibition, increased phenylalanine hydroxylase activity after phosphorylation by cAMP-dependent protein kinase, and a decrease in phenylalanine hydroxylase activity in the presence of the serotonin synthesis inhibitor, alpha-methyl-(DL)-tryptophan are observed. These experiments suggest that the presence of distinct tryptophan hydroxylase enzymes may be evolutionarily conserved and serve as an ancient mechanism to appropriately regulate the production of serotonin in its target tissues.
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PMID:Serotonin synthesis by two distinct enzymes in Drosophila melanogaster. 1582 93