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: EC:4.6.1.2 (guanylate cyclase)
8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitric oxide (NO) acts as a messenger molecule in the CNS by activating soluble guanylyl cyclase. Rat brain synaptosomal NO synthase was stimulated by Ca2+ in a concentration-dependent manner with half-maximal effects observed at 0.3 microM and 0.2 microM when its activity was assayed as formation of NO and L-citrulline, respectively. Cyclic GMP formation was apparently inhibited, however, at Ca2+ concentrations required for the activation of NO synthase, indicating a down-regulation of the signal in NO-producing cells. Purified synaptosomal guanylyl cyclase was not inhibited directly by Ca2+, and the effect was not mediated by a protein binding to guanylyl cyclase at low or high Ca2+ concentrations. In cytosolic fractions, the breakdown of cyclic GMP, but not that of cyclic AMP, was highly stimulated by Ca2+, and 3-isobutyl-1-methylxanthine did not block this reaction effectively. The effects of Ca2+ on cyclic GMP hydrolysis and on apparent guanylyl cyclase activities were abolished almost completely in the presence of the calmodulin antagonist calmidazolium, whose effect was attenuated by added calmodulin. Thus, a Ca2+/calmodulin-dependent cyclic GMP phosphodiesterase is highly active in synaptic areas of the brain and may prevent elevations of intracellular cyclic GMP levels in activated, NO-producing neurons.
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PMID:Regulation of neuronal nitric oxide and cyclic GMP formation by Ca2+. 127 21

1. The mechanical and biochemical effects of agents that relax vascular smooth muscle either through elevation of guanosine 3':5'-cyclic monophosphate (cyclic GMP) or adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels were compared in isolated ring preparations of human umbilical artery and rat aorta. Tone was established by preconstriction with 5-hydroxytryptamine. 2. The endothelium-dependent vasodilator calcium ionophore (A23187) (which stimulates endothelium-derived relaxing factor [EDRF] release and thus acts through soluble guanylyl cyclase), sodium nitroprusside (which stimulates soluble guanylyl cyclase directly), and atrial natriuretic peptide (which stimulates particulate guanylyl cyclase) relaxed rat aorta but not human umbilical artery. 3. Sodium nitroprusside, 10 microM, increased cyclic GMP levels from 10 to 390 pmol mg-1 protein at 2 min in rat aorta, as compared with a slower, relatively attenuated rise from 5 to 116 pmol mg-1 protein after 15 min in human umbilical artery. The rise in cyclic GMP in the umbilical artery was not significantly augmented by the cyclic GMP phosphodiesterase inhibitor, MB22948. Atrial natriuretic peptide increased cyclic GMP levels in rat aorta but not in human umbilical artery. 4. Forskolin, 10 microM, which stimulates both soluble and particulate adenylyl cyclase, maximally relaxed rat aorta and increased cyclic AMP levels from 15 to 379 pmol mg-1 protein at 15 min, but did not significantly relax or increase cyclic AMP levels in human umbilical artery. After preincubation with the cyclic nucleotide phosphodiesterase inhibitor, IBMX, 10 microM forskolin increased cyclic AMP levels to 1365 pmol mg-1 protein at 30 min in human umbilical arteries, but these high levels were not accompanied by mechanical relaxation.5. 8-Bromo-cyclic GMP and 8-bromo-cyclic AMP which are lipophilic analogues of cyclic GMP and cyclic AMP, both maximally relaxed the rat aorta at a concentration of 10 microM, but did not significantly relax the human umbilical artery.6. The findings indicate that elevated cyclic nucleotide levels are not associated with mechanical relaxation of the post-partum human umbilical artery, as in other vessels such as rat aorta. This impaired response to cyclic nucleotides may contribute to closure of the umbilical artery after birth.
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PMID:Impaired cyclic nucleotide-mediated vasorelaxation may contribute to closure of the human umbilical artery after birth. 132 77

Several low molecular weight compounds are capable of activating soluble guanylyl cyclase. Recent evidence suggests that some of these are formed under physiological conditions: the nitric oxide radical, carbon monoxide and the hydroxyl radical. Thus, multiple signal transduction pathways appear to exist that form a family of guanylyl cyclase activating factors and thereby regulate the intracellular cyclic guanosine 3',5'-monophosphate level.
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PMID:NO., CO and .OH. Endogenous soluble guanylyl cyclase-activating factors. 135 61

Guanylyl cyclase from bovine rod outer segments was solubilized using Triton X-100 and a high concentration of KCl, and its regulation was studied. The efficiency of solubilization was about 50-90% of total activity. When the Ca2+ content was lowered (less than 80 nM), guanylyl cyclase was activated about 2-fold. In the presence of higher concentrations of Ca2+ (greater than 140 nM), the activity was decreased. The regulation by Ca2+ was also demonstrated with solubilized preparations. In the presence of 186 nM Ca2+ which inhibited guanylyl cyclase, La3+ activated the enzyme about 2-fold, suggesting that the Ca2(+)-binding protein similar to other Ca2(+)-binding proteins associates with guanylyl cyclase regulation. Sodium nitroprusside and nitric oxide which are activators of soluble guanylyl cyclase in other tissues also activated the retinal guanylyl cyclase. Maximum activation by sodium nitroprusside was 20-fold using Mg2+ as a cofactor. Activation by nitric oxide and related compounds suggests that retinal guanylyl cyclase contains a heme prosthetic group that may participate in a novel regulatory mechanism for this enzyme.
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PMID:Solubilization of guanylyl cyclase from bovine rod outer segments and effects of lowering Ca2+ and nitro compounds. 167 74

L-Arginine (L-Arg) is metabolized by nitric oxide synthase to the reactive intermediate nitric oxide. Since nitric oxide stimulates guanylyl cyclase and cGMP synthesis, L-Arg effects on cGMP accumulation in isolated pancreatic islets of the rat and RINm5F insulinoma cells were determined. Both L-Arg and glucose stimulation increased islet cGMP levels, and glucose potentiated the response to L-Arg alone. A competitive inhibitor of L-Arg metabolism to nitric oxide, NG-monomethyl-L-arginine, reduced glucose- and L-Arg-stimulated insulin release and glucose-induced increases in cGMP; however, basal insulin release was slightly increased. D-Arg and L-ornithine did not affect islet cGMP levels, although insulin release was stimulated. RINm5F cell cGMP levels and insulin release increased in response to L-Arg in a concentration- and time-related manner, whereas glucose and L-histidine were without effect. 8-Bromo-cGMP also slightly increased RINm5F cell insulin release. Sodium nitroprusside as a source of nitric oxide increased RINm5F cell cGMP production. Methylene blue and LY83583, inhibitors of soluble guanylyl cyclase activation, reduced RINm5F cell cGMP levels in the presence and absence of L-Arg; LY83583 also reduced glucose-stimulated cGMP levels in islets. Insulin release by glucose and L-Arg was also inhibited by methylene blue and LY83583 in islets. We conclude that glucose and L-Arg stimulate guanylyl cyclase activity and cGMP formation in beta-cells at least in part through metabolism to the reactive intermediate nitric oxide. However, neither nitric oxide nor cGMP synthesis is obligatory for insulin secretion.
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PMID:L-arginine stimulates cyclic guanosine 3',5'-monophosphate formation in rat islets of Langerhans and RINm5F insulinoma cells: evidence for L-arginine:nitric oxide synthase. 168 79

A cDNA coding for a new subunit of soluble guanylyl cyclase with a calculated molecular mass of 81.7 kDa was cloned and sequenced. On the basis of sequence homology, the new subunit appears to be an isoform of the alpha 1-subunit and was designated alpha 2 as the new subunit is very similar to the alpha 1-subunit in the middle and C-terminal part; it is quite diverse in the N-terminal part. Preceding experiments had shown that coexpression of the alpha 1- and beta 1-subunits is necessary to obtain a catalytically active guanylyl cyclase in COS cells [(1990) FEBS Lett. 272, 221-223]. The finding that the alpha 2-subunit was able to replace the alpha 1- but not the beta 1-subunit in expression experiments demonstrates the interchangeability of the alpha-subunit isoforms of soluble guanylyl cyclase.
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PMID:Molecular cloning and expression of a new alpha-subunit of soluble guanylyl cyclase. Interchangeability of the alpha-subunits of the enzyme. 168 30

We studied the biological activity, stability and interaction of dinitrosyl-iron(II)-L-cysteine with vascular tissue. Dinitrosyl-iron(II)-L-cysteine was a potent activator of purified soluble guanylyl cyclase (EC50 10 nM with and 100 nM without superoxide dismutase) and relaxed noradrenaline-precontracted segments of endothelium-denuded rabbit femoral artery (EC50 10 nM superoxide dismutase). Pre-incubation (5 min; 310 K) of endothelium-denuded rabbit aortic segments with dinitrosyl-iron(II)-L-cysteine (0.036-3.6 mM) resulted in a concentration-dependent formation of a dinitrosyl-iron(II) complex with protein thiol groups, as detected by ESR spectroscopy. While the complex with proteins was stable for 2 h at 310 K, dinitrosyl-iron(II)-L-cysteine in aqueous solution (36-360 microM) decomposed completely within 15 min, as indicated by disappearance of its isotropic ESR signal at gav = 2.03 (293 K). Aortic segments pre-incubated with dinitrosyl-iron(II)-L-cysteine released a labile vasodilating and guanylyl cyclase activating factor. Perfusion of these segments with N-acetyl-L-cysteine resulted in the generation of a low molecular weight dinitrosyl-iron(II)-dithiolate from the dinitrosyl-iron(II) complex with proteins, as revealed by the shape change of the ESR signal at 293 K. The low molecular weight dinitrosyl-iron(II)-dithiolate accounted for an enhanced guanylyl cyclase activation and vasodilation induced by the aortic effluent. We conclude that nitric oxide (NO) produced by, or acting on vascular cells can be stabilized and stored as a dinitrosyl-iron(II) complex with protein thiols, and can be released from cells in the form of a low molecular weight dinitrosyl-iron(II)-dithiolate by intra- and extracellular thiols.
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PMID:The potent vasodilating and guanylyl cyclase activating dinitrosyl-iron(II) complex is stored in a protein-bound form in vascular tissue and is released by thiols. 168 53

The soluble form of guanylyl cyclase-activating-factor (GAF) synthase from rat cerebellum was purified to homogeneity by sequential affinity chromatographic steps on adenosine 2',5'-bisphosphate (2',5'-ADP)-Sepharose and calmodulin-agarose. Enzyme activity during purification was bioassayed by the L-arginine-, NADPH-, and Ca2+/calmodulin-dependent formation of a plasma membrane-permeable nitric oxide-like factor that stimulated soluble guanylyl cyclase in RFL-6 cells. With calmodulin and NADPH as cofactors, purified soluble GAF synthase induced an increase of 1.05 mumol of cGMP per 10(6) RFL-6 cells per 3 min per mg of protein. The coproduct of this signal-transduction pathway appeared to be L-citrulline. GAF synthase catalyzed the conversion of 107 nmol of L-arginine into L-citrulline per min per mg of protein. Based on these assays, this represents a purification of GAF synthase of approximately 10,076- and 8925-fold with recoveries of 16% and 19%, respectively. Rechromatography of the purified enzyme on Mono P (isoelectric point = 6.1 +/- 0.3), Mono Q, and Superose 12 or 6 resulted in no further purification or increase in specific activity. A Stokes radius of 7.9 +/- 0.3 nm and a sedimentation coefficient s20,w of 7.8 +/- 0.2 S were used to calculate a molecular mass of about 279 +/- 25 kDa for the native enzyme. SDS/PAGE revealed a single protein band with a molecular mass of about 155 +/- 3 kDa. These data suggest that soluble GAF synthase purified from rat cerebellum is a homodimer of 155-kDa subunits and that enzyme activity is dependent upon the presence of calmodulin.
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PMID:Purification of a soluble isoform of guanylyl cyclase-activating-factor synthase. 170 96

Soluble guanylyl cyclase was purified from bovine lung by an immunoaffinity chromatographic method using IgG fractions of antisera against a synthetic peptide of the C-terminus of the 70-kDa subunit of the enzyme. After anion-exchange chromatography, the enzyme was bound to an immunoaffinity column and was eluted with the synthetic peptide. This method allowed the convenient isolation of 2 mg of apparently homogeneous enzyme from 40 g cytosolic proteins. The enzyme had an apparent molecular mass of about 150 kDa and consisted of two subunits (70 kDa and 73 kDa) as determined by gel permeation fast protein liquid chromatography and SDS/PAGE. The basal activities determined in the presence of Mg2+ and Mn2+ were 10-20 nmol.min-1.mg-1 and 80-100 nmol.min-1.mg-1, respectively. The enzyme exhibited an ultraviolet-visible absorption spectrum typical for hemoproteins, with a Soret band at 430 nm. The purified enzyme was stimulated by NO-containing compounds. Maximal enzyme activities measured in the presence of sodium nitroprusside were 1.2-2.4 mumol.min-1.mg-1 (half-maximal effect of sodium nitroprusside at 1.3-1.9 microM) and 0.9-1.8 mumol.min-1.mg-1 (half-maximal effect at 0.28-0.41 microM sodium nitroprusside) in the presence of Mg2+ and Mn2+, respectively. The method developed for the large-scale purification of soluble guanylyl cyclase by immunoaffinity chromatography, using synthetic peptides for the elution of the enzyme, appears to be superior to previously described methods. As antibodies against synthetic peptides corresponding to deduced amino acid sequences of the respective protein are easily obtained, the described method may be suitable for a convenient large-scale purification of various proteins.
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PMID:Purification of soluble guanylyl cyclase from bovine lung by a new immunoaffinity chromatographic method. 197 95

On the basis of the conserved amino acid sequences of the catalytic domain of both soluble and plasma membrane forms of guanylyl cyclase, we have used the polymerase chain reaction to identify a new form of guanylyl cyclase that is expressed principally in kidney. The cDNA for this new form (GC-S beta 2) codes for a 76.3-kDa protein, which most closely resembles a 70-kDa subunit (GC-S beta 1) of the lung soluble guanylyl cyclase. The mRNA for GC-S beta 1 is preferentially expressed in lung and brain, whereas GC-S beta 2 mRNA is more abundant in kidney and liver. An 86 amino acid carboxyl-terminal region extends beyond the C-terminus of GC-S beta 1 and contains a consensus sequence (-C-V-V-L) for isoprenylation/carboxymethylation. This is the first demonstration of heterogeneity among the heterodimeric forms of guanylyl cyclase and suggests differential regulation.
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PMID:A new form of guanylyl cyclase is preferentially expressed in rat kidney. 198 Feb 15


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