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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 specificity of binding and the close correlation with alpha-adrenergic receptor-mediated biochemical and physiological responses suggest that the [(3)H]dihydroergocryptine binding site represents, or is closely related to, the human platelet alpha- adrenergic receptors.
Abstract: Human platelets aggregate and undergo a release reaction when incubated with catecholamines. Indirect evidence indicates that these events are mediated through alpha-adrenergic receptors. We used [(3)H]dihydroergocryptine, an alpha-adrenergic antagonist, to identify binding sites on platelets that have the characteristics of alpha-adrenergic receptors. Catecholamines compete for the binding sites in a stereo-specific manner with the potency series of (-) epinephrine > (-) norepinephrine > (+/-) phenylephrine > (-) isoproterenol. The dissociation constant (K(d)) of (-) epinephrine is 0.34 muM. Binding is saturable using a platelet particulate fraction but not with intact platelets. There are 0.130 pmol binding sites per milligram protein in fresh platelet membranes. This number represents approximately 100 binding sites per platelet. The K(d) for [(3)H]-dihydroergocryptine was 0.003-0.01 muM. The alpha-adrenergic antagonist phentolamine (K(d) = 0.0069 muM) was much more potent than the beta-adrenergic antagonist (+/-) propranolol (K(d) = 27 muM) in competing for the binding sites. The binding data were correlated with catecholamine-induced platelet aggregation and inhibition of basal and prostaglandin E(1)-stimulated adenylate cyclase. (-) Epinephrine was more potent than (-) norepinephrine in producing aggregation whereas (-) isoproterenol was ineffective. The threshold dose for inducing aggregation by (-) epinephrine was 0.46 muM. Phentolamine and dihydroergocyrptine blocked this response, whereas (+/-) propranolol had no effect. (-) Epinephrine and (-) norepinephrine inhibited basal and prostaglandin E(1)-stimulated adenylate cyclase in a dose-related manner. The concentration of (-) epinephrine inhibiting adenylate cyclase 50% was 0.7 muM. This inhibition was also blocked by phentolamine and dihydroergocryptine but not by (+/-) propranolol. The specificity of binding and the close correlation with alpha-adrenergic receptor-mediated biochemical and physiological responses suggest that the [(3)H]dihydroergocryptine binding site represents, or is closely related to, the human platelet alpha-adrenergic receptor. The ability to assay this receptor directly and to correlate these data with independently measured sequelae of receptor activation should facilitate increased understanding of the physiology and pathophysiology of the human platelet alpha-adrenergic receptor.
128 citations
TL;DR: The cloning, expression and functional characterization of a DNA from bovine retina that encodes ROS-GC is reported, and the identity of the granylate cyclase (ROS-GC) that synthesizes this pool of cyclic GMP is unknown.
Abstract: In the vertebrate photoreceptor cell, rod outer segment (ROS) is the site of visual signal-transduction process, and a pivotal molecule that regulates this process is cyclic GMP. Cyclic GMP controls the cationic conductance into the ROS, and light causes a decrease in the conductance by activating hydrolysis of the cyclic nucleotide. The identity of the granylate cyclase (ROS-GC) that synthesizes this pool of cyclic GMP is unknown. We now report the cloning, expression and functional characterization of a DNA from bovine retina that encodes ROS-GC.
128 citations
TL;DR: The recently cloned human beta-adrenergic cDNA and several mutated forms expressed in Xenopus laevis oocytes are validated and the utility of the Xenopus oocyte system for studying functional and regulatory properties of receptors coupled to adenylate cyclase is documented, and the possibility that elements in the 5' untranslated region of the beta 2- adrenergic receptor RNA may regulate its translation in vivo is suggested.
128 citations
TL;DR: The detergent, Lubrol-PX, solubilized approximately 90–100% of the particulate adenyl cyclase in cat left ventricular homogenates and revealed a virtual absence of particulate material in the ultracentrifuge supernatants.
127 citations
TL;DR: A new rapid and reliable assay for guanylate cyclase was established, which employs a simple procedure to isolate guanosine 3' : 5'-monophosphate with neutral aluminum oxide and Dowex 1 formate columns.
127 citations