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: A correlation between phosphorylation and complete glycosylation of NPR-A is suggested and that both are required for hormone-induced enzymatic activity.
107 citations
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TL;DR: Results show that muscarinic acetylcholine receptors mediate both transient and long-lived effects on adenylate cyclase activity that resemble those of opiates.
Abstract: Carbachol, an activator of muscarinic acetylcholine receptors of NG108-15 hybrid cells, inhibits adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] rapidly and reversibly and slowly evokes a 200-300% increase in adenylate cyclase activity over a period of 24-30 hr. Both the inhibition of adenylate cyclase and the gradual increase in enzyme activity are dependent on muscarinic acetylcholine receptors and the receptor activator. Withdrawal of carbachol results in a gradual return of adenylate cyclase activity to control levels over a period of 6 hr; the half-life for decay of enzyme activity is 1.6 hr. These results show that muscarinic acetylcholine receptors mediate both transient and long-lived effects on adenylate cyclase activity that resemble those of opiates.
107 citations
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TL;DR: The omission of the NTP-regenerating system from cyclase reactions strongly reduced the potencies of MANT-ADP, indicative for phosphorylation to Mant-ATP by pyruvate kinase.
107 citations
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TL;DR: Different mechanical, i.e., negative inotropic effects of adenosine and its analogs in the heart are observed in auricular preparations only and are unlikely to be related to the cAMP and/or cGMP system.
Abstract: The effects of adenosine, the Ri site adenosine receptor agonist (-)-N6-phenylisopropyladenosine (PIA), the Ra site agonist 5'-N-ethylcarboxamideadenosine (NECA) and the P site agonist 2',5'-dideoxyadenosine (DIDA) on force of contraction, cyclic AMP (cAMP) and cyclic GMP (cGMP) content and on transmembrane action potential were studied in isolated electrically driven left auricles and papillary muscles from guinea pigs. Furthermore, the effects on adenylate cyclase activity in a particulate membrane preparation were investigated. In the auricles, adenosine, PIA and NECA had negative inotropic effects which were accompanied by a shortening of the action potential. Theophylline antagonized these effects which are likely mediated by R site adenosine receptors. DIDA was ineffective. Except for a small positive inotropic effect of adenosine the analogs were ineffective in the papillary muscles. None of the mechanical effects was accompanied by a change in cAMP and cGMP content in the intact preparations. In the broken cell preparation PIA and NECA had no effect on adenylate cyclase activity. Adenosine and DIDA inhibited the enzyme. The latter effects can be classified as P site-mediated effects. In conclusion, distinct mechanical, i.e., negative inotropic effects of adenosine and its analogs in the heart are observed in auricular preparations only. These effects are unlikely to be related to the cAMP and/or cGMP system. Instead, they are probably due to a direct shortening of the action potential which, in turn, is conceivably due to an increase in K+ outward current and a secondary decrease in Ca++ inward current. This effect is apparently mediated by cardiac R site adenosine receptors which are not detectably coupled to adenylate cyclase.
107 citations
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TL;DR: It is concluded that Ca2+, which confers more helical structure to the activator, converts the inactive, less helical structures to the active, more helicals structure, and that chemical modification of the activators leading to unfolding of the molecule abolishes its biological activity.
107 citations