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)

Guanylate cyclase is found in virtually all cells, but its physiologic role and the effect of hormones on its activity have not been clarified. Hepatic soluble guanylate cyclase activity (37,000 g supernatant) in rats with diabetes-mellitus-like syndrome induced by streptozotocin, 65 mg./kg. i.v., was 140 +/- 8 pmoles accumulated/mg. protein/10 min. (n = 13 rats) as against 279 +/- 16 pmoles accumulated/mg. protein/10 min. (n = 12 rats) in normal rats. The average blood sugar for the 12 normal rats was 100 +/- 4 mg./100 ml. and 546 +/- 32 mg./100 ml. for 13 diabetic rats. The decreased soluble hepatic guanylate cyclase activity in diabetic rats was completely restored to normal with 10 U. regular insulin, i.p. The maximum increase in guanylate cyclase activity was observed as early as five minutes and as late as two hours after insulin administration. Insulin restoration of guanylate cyclase was dose-related over a range of 1 U. to 10 U., i.p. Hepatic cyclic GMP levels in vivo paralleled in-vitro guanylate cyclase activity, being 29 +/- 0.4 pmoles/gm. wet weight in normals, 17 +/- 0.4 pmoles/gm. wet weight in streptozotocin-diabetic rats, and 38 +/- 0.4 pmoles/gm. wet weight two hours after the injection of 10 U. regular insulin. We conclude that rat hepatic guanylate cyclase is decreased in streptozotocin-induced diabetes and that insulin modulates this enzyme. The administration of exogenous insulin in normal animals did not further augment hepatic guanylate cyclase activity.
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PMID:Decreased rat hepatic guanylate cyclase activity in streptozotocin-induced diabetes mellitus. 1 59

Guanylate cyclase activities were identified in a soluble fraction and a particular fraction obtained from the Arteria coronaria of cattle. The Km-value was 1.0 +/- 0.7 - 10(-4) M for the enzyme substrate complex of the guanylate cyclase of the soluble fraction and 9.2 +/- 1.5 - 10(-4) M for the particular fraction. For the enzyme activity of the soluble fraction Mn++ cannot be replaced by Ca++ or Mg++, whereas for the enzyme activity of the particulate fraction Mn++ can be replaced by Mg++ but not by Ca++. The guanylate cyclase of the particulate fraction can be activated by acetylcholine. This activation can be cancelled by atropine. Acetylcholine exerts no influence on the guanylate cyclase activity of the soluble fraction. ATP inhibits the enzyme activities of both fractions whereas cAMP shows no influence on the guanylate cyclase activity.
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PMID:[Proof of guanylate cyclase activity in the coronary artery of cattle]. 1 86

Guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] activity of human platelet homogenates was stimulated by the addition of phospholipase A2 or unsaturated fatty acids such as oleic, vaccenic, linoleic, linolenic, eicosenoic, eicosadienoic, and arachidonic acids. The addition of lipoxidase potentiated the fatty acid-induced stimulation of guanylate cyclase purified by DEAE-cellulose column chromatography. The extent of the stimulation was dependent on the concentration of the oxidized form of these fatty acids (peroxides). Saturated fatty acids such as stearic and arachidic acids had no effect on the guanylate cyclase activity in the presence or absence of lipoxidase, indicating that human plateletguanylate cyclase is stimulated by unsaturated fatty acid peroxides rather than by fatty acids. Hemoglobin prevented the enzyme stimulation produced by low concentrations of fatty acid peroxides, but enhanced stimulation of the enzyme activity with high concentrations of fatty acid peroxides. 2-Mercaptoethanol, dithiothreitol, and N-ethylmaleimide inhibited the guanylate cyclase activities both in the presence and absence of unsaturated fatty acidperoxide. The stimulation of guanylate cyclase activity by unsaturated fatty acid peroxidesis attributed to oxidation of sulfhydryl residues of the enzyme protein.
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PMID:Stimulation of human platelet guanylate cyclase by unsaturated fatty acid peroxides. 2 Jun 30

Highly purified EF-Ts from E. coli does contain guanylate cyclase activity, which is absent from other purified transfer factors, such as EF-Tu and EF-G. Guanylate cyclase activity has been characterized by its sensitivity to inhibitors and substrate specificity. Although the physicochemical properties of guanylate cyclase are closely related to those of EF-Ts, it does not appear to be a contaminant of this transfer factor, but a specific enzyme. The possible role of guanylate cyclase in protein synthesis is discussed.
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PMID:[Guanyl cyclase activity in the EF-T elongation factor of Escherichia coli]. 2 Oct 22

Partially purified soluble rat liver guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] was activated by superoxide dismutase (superoxide: superoxide oxidoreductase, EC 1.15.1.1). This activation was prevented with KCN or glutathione, inhibitors of superoxide dismutase. Guanylate cyclase preparations formed superoxide ion. Activation by superoxide dismutase was further enhanced by the addition of nitrate reductase. Although guanylate cyclase activity was much greater with Mn2+ than with Mg2+ as sole cation cofactor, activation with superoxide dismutase was not observed when Mn2+ was included in incubations. Catalase also decreased the activation induced with superoxide dismutase. Thus, activation required the formation of both superoxide ion and H2O2 in incubations. Activation of guanylate cyclase could not be achieved by the addition of H2O2 alone. Scavengers of hydroxyl radicals prevented the activation. It is proposed that superoxide ion and hydrogen peroxide can lead to the formation of hydroxyl radicals that activate guanylate cyclase. This mechanism of activation can explain numerous observations of altered guanylate cyclase activity and cyclic GMP accumulation in tissues with oxidizing and reducing agents. This mechanism will also permit physiological regulation of guanylate cyclase and cyclic GMP formation when there is altered redox or free radical formation in tissues in response to hormones, other agents, and processes.
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PMID:Activation of guanylate cyclase by superoxide dismutase and hydroxyl radical: a physiological regulator of guanosine 3',5'-monophosphate formation. 2 77

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

Guanylate cyclase (GTP pyrophosphate-lyse (cyclizing), EC 4.6.1.2.) of bovine retinal rod outer segments is almost completely particulate, i.e. associated with rod outer segment membranes. In contrast to particulate guanylate cyclase in other tissues, treatment of rod outer segments with Triton X-100 does not solublize the enzyme but inhibits it. Enzyme activity is dependent on the presence of divalent cation, especially Mn2+ with only poor activation by Mg2+ (10-fold lower) and no activation seen with other cation. Ezpression of maximal activity required Nm2+ and GTP in equimolar concentrations with an apparent Km of 8 . 10(-4) M and V of 10 nmol/min per mg protein. Excess of Mn2+ over that required for the formation of the Mn . GTP complex was inhibitory. Ca2+, Ba2+ and Co2+ inhibited enzyme activity when assayed with the Mn . GTP substrate complex. In the presence of a fixed concentration of 1mM Mn2+, the enzyme exhibited strong negative cooperative interactions with GTP, characterized by an intermediary plateau region in the substrate vs. enzyme activity curve, a curve of downward concavity in the double reciprocal plot and a Hill coefficient of 0.5. Nucleotides such as ITP, ATP and UTP at higher concentrations (1 mM) stimulates activity by 40%. NaN3 has no effect on the guanylate cyclase. It is thus possible that the guanylate cyclase may be regulated in vivo by both the metal : GTP substrate ratio and the free divalent cation concentration as well as by the ATP concentration and thus play an important but yet undefined role in the visual process.
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PMID:Characterization of guanylate cyclase of rod outer segments of the bovine retina. 2 9

A partially purified preparation of the heat-stable enterotoxin of Escherichia coli caused a rapid and persistent increase in electric potential difference and short-circuit current when added in vitro to the luminal surface of isolated rabbit ileal mucosa. As little as 1 ng/ml produced an easily detectable response. Under short-circuit condition, the enterotoxin abolished net Cl- absorption; this change was half that produced by theophylline, which stimulated net secretion. The enterotoxin did not change cyclic AMP concentration but caused large and persistent increases in cyclic GMP concentration. The electrical and nucleotide responses exhibited similar and unusually broad concentration-dependences and maximal effects could not be demonstrated. Theophylline elevated cyclic GMP concentration 3-fold both in the presence and absense of the enterotoxin, suggesting no effect of the toxin on cyclic GMP phosphodiesterase. Guanylate cyclase [GTP pyrophosphatelyase(cyclizing); EC 4.6.1.2] activity in a crude membrane fraction from intestinal epithelial cells was stimulated 7-fold by the enterotoxin. These results suggest that guanylate cyclase stimulation is the basis for the toxin's diarrheagenic effect.
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PMID:Heat-stable enterotoxin of Escherichia coli: in vitro effects on guanylate cyclase activity, cyclic GMP concentration, and ion transport in small intestine. 2 15

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

Guanylate cyclase activity has been studied in muscle of normal subjects and of patients suffering from muscular and neuromuscular diseases. In normal tissue a guanylate cyclase activity was found in both soluble and particulate fractions of homogenate. We found also that the kinetic analysis of the enzyme of soluble differed from that of particulate fraction. A decrease of guanylate cyclase activity in crude homogenate was observed in muscular dystrophies, in neuromuscular atrophies, and in inflammatory forms of muscle disease.
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PMID:Guanylate cyclase activity in normal and diseased human muscle. 2 81


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