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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: It is shown that olfactory responses may be mediated by a GTP-binding protein (G protein), a homolog of the visual, hormonal, and brain signal transducing polypeptides.
Abstract: The sense of smell involves the stimulation of sensory neurons by odorants to produce depolarization and action potentials. We show that olfactory responses may be mediated by a GTP-binding protein (G protein), a homolog of the visual, hormonal, and brain signal transducing polypeptides. The olfactory G protein is identified in isolated dendritic membranes (olfactory cilia preparations) of chemosensory neurons from three vertebrate species and is shown to mediate the stimulation by odorants of the highly active adenylate cyclase in these membranes. The G protein of olfactory neurons is most similar to Gs, the hormonal stimulatory GTP-binding protein. Its alpha subunit has a molecular weight of about 42,000, and it undergoes ADP-ribosylation catalyzed by cholera toxin that leads to adenylate cyclase activation. The slight difference in molecular weights of the frog olfactory and the liver Gs alpha subunits and the higher sensitivity of olfactory adenylate cyclase to nonhydrolyzable GTP analogs are consistent with the possible existence of different Gs variants. Signal amplification due to the olfactory G protein may be responsible for the unusual acuity of the sense of smell.
102 citations
TL;DR: The results are consistent with the idea that 5-HT has two actions: one is to stimulate the enzyme adenyl cyclase to synthesize cyclic AMP, which, in turn, stimulates cation transport, and the other is to increase anion transport by a mechanism which is independent of cyclicAMP.
Abstract: 1. The role of cyclic AMP in mediating the action of 5-HT on salivary glands has been studied by measuring transepithelial potentials. 2. The lumen of unstimulated glands is 4 mV positive but becomes 12 mV negative after treatment with 5-HT (10 -8 M). Both the potential and the secretory responses to 5-HT are dose-dependent over the same concentration range. 3. The electrical response of salivary glands to cyclic AMP is qualitatively different to that of 5-HT; instead of going negative the potential goes more positive. 4. An increase in positive potential is also observed after treatment with theophylline (10 -2 M), or when glands are stimulated with 5-HT in a chloride-free saline. 5. These results are consistent with the idea that 5-HT has two actions. One is to stimulate the enzyme adenyl cyclase to synthesize cyclic AMP, which, in turn, stimulates cation transport. The other is to increase anion transport by a mechanism which is independent of cyclic AMP.
102 citations
TL;DR: In membrane preparations ofhuman platelets, whose adenylate cyclase is inhibited by a-adrenergic agonists in a GTP-dependent manner, the influence of epinephrine on GTPase activity is studied and it is reported here that epinphrine inhibits adenolatecyclase and stimulates a low Km GTP enzyme via cy-adRenoceptors in this system.
102 citations
TL;DR: The maturation of rat reticulocytes to erythrocytes is paralleled by a marked loss of adenylate cyclase responsiveness to catecholamines and guanine nucleotides without significant loss of basal enzyme activity, which suggests that one molecular concomitant of rat ERYthrocyte maturation is a decrease in the effectiveness of receptor-guanineucleotide regulatory protein communication.
102 citations
TL;DR: Investigations have shown that the enzyme is regulated by short term mechanisms that may involve activation of adenyl cyclase or protein kinase C and a long-term mechanism of activation by altered gene expression has also been suggested.
Abstract: 1. Aromatic L-amino acid decarboxylase is the enzyme responsible for the decarboxylation step in both the catecholamine and the indolamine synthetic pathways. Immunological and molecular biological studies suggest that it is a single enzyme with one catalytic site but with different locations for attachment of the substrates. The enzyme is widely distributed in the brain and in peripheral tissues. 2. Recent investigations have shown that the enzyme is regulated by short term mechanisms that may involve activation of adenyl cyclase or protein kinase C. In addition, a long-term mechanism of activation by altered gene expression has also been suggested.
102 citations