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)

Crude preparations of secretin or pancreozymin increased and at higher concentrations decreased guanylate cyclase (GTP pyophosphate-lyase, EC 4.6.1.2) activity from soluble and particulate fractions of rat liver homogenates. Partially purified and synthetic secretin were without effect as was the biologically active octapeptide fragment of pancreozymin. The active contaminants in these preparations survived boiling, saponification, and treatment with phospholipase A, trypsin and neuraminidase C. The activity was extractable with chloroform/methanol and did not survive ashing. Eight bile salt contaminants in crude secretin were obtained with thin-layer chromatography. Two of the contaminating bile salts that increased liver particulate guanylate cyclase activity were identified as taurodeoxycholate and either glycochenodeoxycholate or glycodeoxycholate; taurocholate was inhibitory. The sodium salts of cholate, deoxycholate, chenodeoxycholate and their glycine-or taurine-conjugated forms either increased or decreased particulate and soluble rat liver guanylate cyclase activity depending upon their concentration. Thus, the previously reported stimulatory and inhibitory effects of secretin and pancreozymin preparations on guanylate cyclase activity are probable attributable to their bile salt contaminants.
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PMID:Activation of liver guanylate cyclase by bile salts and contaminants in crude secretin and pancreozymin preparations. 1 19

Nitric oxide gas (NO) increased guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] activity in soluble and particulate preparations from various tissues. The effect was dose-dependent and was observed with all tissue preparations examined. The extent of activation was variable among different tissue preparations and was greatest (19- to 33-fold) with supernatant fractions of homogenates from liver, lung, tracheal smooth muscle, heart, kidney, cerebral cortex, and cerebellum. Smaller effects (5- to 14-fold) were observed with supernatant fractions from skeletal muscle, spleen, intestinal muscle, adrenal, and epididymal fat. Activation was also observed with partially purified preparations of guanylate cyclase. Activation of rat liver supernatant preparations was augmented slightly with reducing agents, decreased with some oxidizing agents, and greater in a nitrogen than in an oxygen atmosphere. After activation with NO, guanylate cyclase activity decreased with a half-life of 3-4 at 4 degrees but re-exposure to NO resulted in reactivation of preparations. Sodium azide, sodium nitrite, hydroxylamine, and sodium nitroprusside also increased guanylate cyclase activity as reported previously. NO alone and in combination with these agents produced approximately the same degree of maximal activation, suggesting that all of these agents act through a similar mechanism. NO also increased the accumulation of cyclic GMP but not cyclic AMP in incubations of minces from various rat tissues. We propose that various nitro compounds and those capable of forming NO in incubations activate guanylate cyclase through a similar but undefined mechanism. These effects may explain the high activities of guanylate cyclase in certain tissues (e.g., lung and intestinal mucosa) that are exposed to environmental nitro compounds.
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PMID:Nitric oxide activates guanylate cyclase and increases guanosine 3':5'-cyclic monophosphate levels in various tissue preparations. 2 Jun 23

Sarcolemma was isolated by fractionation of salt-extracted particles on two consecutive sucrose density gradients. Salt extraction of homogenates, rather than of washed particles, was found to preserve the activities of adenylate cyclase and ouabain-sensitive (Na+,-K+)-ATPase in the isolated sarcolemmal membranes. Purified sarcolemma contained substantial adenylate cyclase and guanylate cyclase activities that were stimulable by beta-adrenergic and muscarinic agonists, respectively. Significant ouabain-sensitive (Na+, K+)-ATPase activity as well as putative digitalis receptor activity was also present in sarcolemma. Cyclic nucleotide phosphodiesterases of sarcolemma, both cAMP- and cGMP-dependent, displayed positive cooperativity of substrate interactions; Ca2+ ions were found to increase the activity of the GMP-dependent enzyme.
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PMID:Isolation and enzymatic characterization of guinea pig cardiac sarcolemma. 2 1

Kinetic properties of guanylate cyclase present in the washed particles, plasma membranes, and the soluble cytoplasm of heart and skeletal muscle are described; properties of the enzyme solubilized by Triton X-100 treatment of the particles or membrane fractions are also reported. It is apparent from the data that the membrane-bound guanylate cyclase in the cell may be regulated by acetylcholine, may exist as a metallo-protein with bound Mn2+ (essential for activity), and that Mg2+ regulates, whereas Ca2+ and nucleotides (especially ATP) modulate, guanylate cyclase activity. The findings also suggest that guanylate cyclase, similar to adenylate cyclase and (Na+, K+)-ATPase, is mainly located in the plasma membranes of heart and skeletal muscle.
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PMID:Properties of membrane-bound and soluble guanylate cyclase of cardiac and skeletal muscle. 2 2

Guanylate cyclase in the guinea pig fundic mucosa occurred in two enzymatic forms: a "soluble" form and a particulate form. The mean basal activity of the soluble fraction measured in the presence of 300 micrometer guanosine-5'-triphosphate and 5 mM MnCl2 was 72.6 +/- 5.3 pmoles of cyclic GMP per mg of protein per min. Guanylate cyclase activity was dependent on Mn2+; it was increased by sodium azide (NaN3), CaCl2, cysteine, secretin, and cholecystokinin, but it was not influenced by gastrin, histamine, cholinergic esters, prostaglandins E1 and A1. NaN3 (1 mM) decreased the apparent Km for MnCl2 and potentiated the effects of MgCl2. The activity of the particulate fraction represented about 14% of that of the supernatant fraction. The guanylate cyclase activity of that fraction was not modified by NaN3, gastrin, cholinergic agents, secretin, or cholecystokinin. Cysteine inhibited its activity. These data do not support the hypothesis that cyclic GMP acts as a second messenger for the action of cholinergic agents and gastrin in the guinea pig gastric mucosa.
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PMID:Effect of Ca2+, Mg2+, NaN3, cholinergic agents, and gastrointestinal hormones on the guanylate cyclase from guinea pig gastric mucosa. 2 35

The effects of a variety of agents on guanylate cyclase activity were tested in broken cell preparations of mammary glands from midpregnant mice. Of the agents tested, only phospholipase A, triton X-100, and an impure egg lysolecithin preparation enhanced the activity of guanylate cyclase in mammary gland homogenates; other agents, including sodium azide and phospholipase C, and purified egg lysolecithin had no effect. Phospholipase A increased the activity of guanylate cyclase in the 150,000 g pellet fractions of mammary gland homogenates, bud did not consistently enhance guanylate cyclase in the 150,000 g supernatant fractions. Phospholipase A did not appear to enhance guanylate cyclase activity by solublizing the enzyme from the 150,000 g pellet. Triton X-100, in contrast, appeared to act by solubilizing guanylate cyclase from the material present in the 150,000 g pellet. Triton X-100 increased by several fold guanylate cyclase activity in the tissue homogenates and the 150,000 g pellets, but did not consistently enhance enzyme activity in the 150,000 g supernatant. Triton X-100 had no effect on the apparent Km of guanylate cyclase.
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PMID:Effects of phospholipase A and triton x-100 on guanylate cyclase activity in mammary gland homogenates from mice. 2 72

Guanylate cyclase (GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2) was purified 2250-fold from the synaptosomal soluble fraction of rat brain. The specific activity of the purified enzyme reached 41 nmol cyclic GMP formed per min per mg protein at 37 degrees C. In the purified preparation, GTPase activity was not detected and cyclic GMP phosphodiesterase activity was less than 4% of guanylate cyclase activity. The molecular weight was approx. 480 000. Lubrol PX, hydroxylamine, or NaN3 activated the guanylate cyclase in crude preparations, but had no effect on the purified enzyme. In contrast, NaN3 plus catalase, N-methyl-N'-nitro-N-nitrosoguanidine or sodium nitroprusside activated the purified enzyme. The purified enzyme required Mn2+ for its activity; the maximum activity was observed at 3-5 mM. Cyclic GMP activated guanylate cyclase activity 1.4-fold at 2 mM, whereas inorganic pyrophosphate inhibited it by about 50% at 0.2 mM. Guanylyl-(beta,gamma-methylene)-diphosphonate and guanylyl-imidodiphosphate, analogues of GTP, served as substrates of guanylate cyclase in the purified enzyme preparation. NaN3 plus catalase or N-methyl-N'-nitro-N-nitrosoguanidine also remarkably activated guanylate cyclase activity when the analogues of GTP were used as substrates.
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PMID:Purification and properties of guanylate cyclase from the synaptosomal soluble fraction of rat brain. 2 67

The soluble form of guanylate cyclase from rat lung has been purified approximately 23,000-fold to homogeneity by isoelectric precipitation, GTP-Sepharose chromatography, and preparative gel electrophoresis. A single protein-staining band is observed after analytical gel electrophoresis on either 4 or 7.5% polyacrylamide gels. The final purified enzyme has a specific activity of about 700 nmol of cyclic GMP formed/min/mg of protein at 37 degrees C in the presence of 4.8 mM MnCl2 and 100 micrometer GTP. Bovine serum albumin appears to slightly increase guanylate cyclase activity, but mainly stabilizes the purified enzyme; in its presence, specific activities in excess of 1 mumol of cyclic GMP formed/min/mg of enzyme protein can be obtained. When Mg2+ or Ca2+ are substituted for Mn2+, specific activities decrease to approximately 21 and 40 nmol of cyclic GMP formed/min/mg of protein, respectively. The apparent Michaelis constant for MnGTP in the presence of 4.8 mM MnCl2 is 10.2 micrometer. Kinetic patterns on double reciprocal plots as a function of free Mn2+ are concave downward. The native enzyme has a molecular weight of approximately 151,000 as determined on Sephacryl S-200; sodium dodecyl sulfate-polyacrylamide gel electrophoresis results in two protein-staining bands with approximate molecular weights of 79,400 and 74,000. Thus, it appears that the soluble form of guanylate cyclase from rat lung exists as a dimer.
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PMID:Purification of soluble guanylate cyclase from rat lung. 3 65

The electron cytochemical method of guanylate cyclase demonstrated a number of advantages making possible differentiation between the plasmalemmal, cytoplasmic, nucleoplasmic, and nucleolar localization of the enzyme. This method permitted to reveal that the enzyme possessed organ specificity of distribution in the cell and could be activated by a specific activator--sodium azide. The distribution of guanylate cyclase strictly correlated with the functional state of the cell.
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PMID:[Submicroscopic features of guanylate cyclase detection in mammalian epithelial and myocardial cells]. 3 39

The mature rat testis contains both a soluble guanylate cyclase and a soluble adenylate cyclase. Both these soluble enzymes prefer manganous ion for activity. It is known that guanylate cyclase can, when activated by a variety of agents, catalyze the formation of cyclic AMP. The following experiments were performed to determine whether the testicular soluble adenylate and guanylate cyclase activities were carried on the same molecule. Analysis of supernatants from homogenized rat testis by gel filtration and sucrose density gradient centrifugation showed that the two activities were clearly separable. The molecular weight of guanylate cyclase is 143 000, while that of adenylate cyclase is 58 000. Treatment of the column fractions with 0.1 mM sodium nitroprusside allowed guanylate cyclase activity to be expressed with Mg(2+) as well as with Mn(2+). Sodium nitroprusside did not affect the metal ion or substrate specificity of adenylate cyclase. These experiments show that adenylate and guanylate cyclase activities are physically separable.
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PMID:Separation of soluble adenylate and guanylate cyclases from the mature rat testis. 3 43


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