Topic
Cyclase
About: Cyclase is a research topic. Over the lifetime, 10162 publications have been published within this topic receiving 388566 citations.
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TL;DR: The activation of adenylate cyclase by vasoactive intestinal peptide was used as a model to investigate the molecular mechanisms triggered by the occupancy of dopamine recognition sites in rat anterior pituitary, and it is inferred that stimulation of D-2 (dopamine) receptors may affect pituitaries secretion by inhibiting the activation of anterior pituitsary adenYLatecyclase by VIP or other secretagogues.
Abstract: The activation of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] by vasoactive intestinal peptide (VIP) was used as a model to investigate the molecular mechanisms triggered by the occupancy of dopamine recognition sites in rat anterior pituitary. Dopamine failed to change the basal enzyme activity, but it inhibited the stimulation of adenylate cyclase elicited by VIP. Apomorphine, 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene, and 2-bromo-alpha-ergocryptine mimicked the effect of dopamine, whereas (-)-sulpiride and and classical neuroleptics antagonized it. Dopamine failed to modulate the activation of pituitary adenylate cyclase by prostaglandin E1, which does not increase prolactin secretion. From these results we infer that stimulation of D-2 (dopamine) receptors may affect pituitary secretion by inhibiting the activation of anterior pituitary adenylate cyclase by VIP or other secretagogues.
116 citations
TL;DR: A soluble enzyme preparation from immature sage leaves has been shown to catalyze the cation-dependent cyclization of geranyl pyrophosphate to the isomeric monoterpene olefins (+/-)-alpha-pinene and (-)-beta- pinene and to lesser amounts of camphene and limonene.
116 citations
TL;DR: It is found that K‐opiate receptors are negatively coupled to adenylate cyclase, and the pattern of heterologous desensitization suggests that chronic exposure to K opiates leads to alterations in postreceptor regulatory components, possibly GTP‐binding proteins.
Abstract: The nature of the opiate modulation of adenylate cyclase following acute and chronic agonist exposure has been investigated in rat spinal cord. Using membranes of both adult rat spinal cord and spinal cord-dorsal root ganglion cocultures, we found that kappa-opiate receptors are negatively coupled to adenylate cyclase. The kappa-opiate agonists (e.g., U50488) inhibit significantly and dose-dependently the basal and the forskolin-stimulated cyclase activities, whereas mu and delta agonists are ineffective. The regulatory action is stereospecific and requires the presence of GTP. EGTA treatment of the plasma membranes abolished the effect of kappa-opiate agonists on the basal cyclase activity, and this inhibitory effect could not be restored by subsequent addition of Ca2+. The EGTA treatment did not affect the kappa agonist inhibition of the forskolin-stimulated cyclase. The results also show that following chronic exposure of cultured cells to etorphine or U50488, there is a loss of kappa agonist inhibition of the cyclase. Moreover, this desensitization process appears to be heterologous, because alpha 2-adrenergic agonists (e.g., clonidine or norepinephrine) and the muscarinic agonist (carbachol) exhibited significantly lower potency for inhibiting cyclase activity when compared to untreated cultures. This pattern of heterologous desensitization suggests that chronic exposure to kappa opiates leads to alterations in postreceptor regulatory components, possibly GTP-binding proteins.
115 citations
TL;DR: Bovine taste buds bearing papillae exhibit high adenyl cyclase activity comparable to the activity found in the brain, while the tongue epithelium without taste buds exhibits much lower activity.
115 citations
TL;DR: An ancient evolutionary origin of this stress-signaling cascade in a common precursor of modern Metazoa and Metaphyta is suggested, which is reminiscent of the drought stress signaling pathway in plants.
Abstract: Sponges (phylum Porifera) are the phylogenetically oldest metazoan animals, their evolution dating back to 600 million years ago. Here we demonstrate that sponges express ADP-ribosyl cyclase activity, which converts NAD(+) into cyclic ADP-ribose, a potent and universal intracellular Ca(2+) mobilizer. In Axinella polypoides (Demospongiae, Axinellidae), ADP-ribosyl cyclase was activated by temperature increases by means of an abscisic acid-induced, protein kinase A-dependent mechanism. The thermosensor triggering this signaling cascade was a heat-activated cation channel. Elucidation of the complete thermosensing pathway in sponges highlights a number of features conserved in higher organisms: (i) the cation channel thermoreceptor, sensitive to heat, mechanical stress, phosphorylation, and anesthetics, shares all of the functional characteristics of the mammalian heat-activated background K(+) channel responsible for central and peripheral thermosensing; (ii) involvement of the phytohormone abscisic acid and cyclic ADP-ribose as its second messenger is reminiscent of the drought stress signaling pathway in plants. These results suggest an ancient evolutionary origin of this stress-signaling cascade in a common precursor of modern Metazoa and Metaphyta.
115 citations