共查询到20条相似文献,搜索用时 31 毫秒
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The natural occurrence of cyclic nucleotides in higher plants, formerly a topic of fierce debate, is now established, as is the presence of nucleotidyl cyclases and cyclic nucleotide phosphodiesterases capable of their synthesis and breakdown. Here we describe the significant properties of cyclic nucleotides, also outlining their second messenger functions and the history of plant cyclic nucleotide research over its first three decades. Findings of the last five years are detailed within the context of the functional role of cyclic nucleotides in higher plants, with particular emphasis upon nucleotidyl cyclases and cyclic nucleotide-responsive protein kinases, -binding proteins and -gated ion channels, with future objectives and strategies discussed. 相似文献
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Cyclic GMP transporters 总被引:4,自引:0,他引:4
Sager G 《Neurochemistry international》2004,45(6):865-873
The biokinetics of guanosine 3',5'-cyclic monophosphate (cGMP) is characterized by three distinct processes: synthesis by guanylate cyclases (GCs), conversion of cGMP to GMP by cyclic nucleotide phosphodiesterases (PDEs) and the excretion of unchanged cGMP by transport proteins in the cell membrane. Efflux is observed in virtually all cell types including cells which originate from brain. Studies of intact cells, in which metabolic inhibitors and probenecid reduced extrusion of cGMP and wherein cGMP was extruded against concentration gradients, indicated the existence of ATP requiring organic anion transport system(s). Functional studies of inside-out vesicles have revealed cGMP transport systems wherein translocation is coupled to hydrolysis of ATP. The extrusion of cGMP is inhibited by a number of unrelated compounds and this indicates that cGMP is substrate for multispecific transporters. Recent transfection studies suggest that members of the MRP (multidrug resistance protein) family; MRP4, MRP5 and MRP8 translocate cGMP across the cell membrane. Many of the MRPs have been detected in brain. In addition tertiary active transport by the organic anion transporter family has also been identified. At least one member (OAT1) shows relative high affinity for cGMP and is also expressed in brain. The biological significance of cGMP transporters has to be clarified. Their role in cGMP biokinetics, being responsible for one of the cellular elimination pathways, is well established. However, there is growing evidence that extracellular cGMP has effects on cell physiology and pathophysiology by an auto- or paracrine mechanism. 相似文献
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Vincent Madison 《Biopolymers》1985,24(1):97-103
A multistep computational scheme was used to deduce possible conformations for a cyclic antagonist analog of somatostatin that has been reported by Coy and coworkers. An algebraic algorithm was used to find dihedral angles that give cyclic structures, the energy was computed for these structures, the lower-energy structures were classified into conformational families, the energy was minimized for the lowest-energy member of each family, and finally, the structures from energy minimization were reclassified. Analysis revealed seven distinct conformational families that contain reverse turns. The families differ in the position of the turns in the primary sequence; frame-shifted turns are observed at each possible position. 相似文献
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Cyclic change-over designs 总被引:1,自引:0,他引:1
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SHUZO KUDO KINYA NAKAZAWA YOSHINORI NOZAWA 《The Journal of eukaryotic microbiology》1980,27(3):342-345
SYNOPSIS. Cyclic nucleotide phosphodiesterase [EC 3.1.4.17] was examined in Tetrahymena pyriformis strain NT-1. Enzymic activity was associated with the soluble and the particulate fractions, whereas most of the cyclic GMP phosphodiesterase activity was localized in the soluble fraction: the activities were optimal at pH 8.0–9.0. Although very low activities were detected in the absence of divalent cations, they were significantly increased by the addition of either Mg2+ or Mn2-. A kinetic analysis of the properties of the enzymes yielded 2 apparent KIII values ranging in concentration from 0.5 to 50 μM and from 0.1 to 62 μ M for cyclic AMP and GMP. respectively. A Ca2+-dependent activating factor for cyclic nucleotide phosphodiesterase was extracted from Tetrahymena cells, but this factor did not stimulate guanylate cyclase [EC 4.6.1.2] activity in this organism. On the other hand, Tetrahymena also contained a protein activator which stimulated guanylate cyclase in the presence of Ca2+, although this activator did not stimulate the phosphodiesterase. the results suggested that Tetrahymena might contain 2 types of Ca2+-dependent activators, one specific for phosphodiesterase and the other for guanylate cyclase. 相似文献
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Growth Control and Cyclic Alterations of Cyclic AMP in the Cell Cycle 总被引:44,自引:0,他引:44
MAX M. BURGER BERND M. BOMBIK BRUCE McL. BRECKENRIDGE J. R. SHEPPARD 《Nature: New biology》1972,239(93):161-163
Growth stimulated by protease treatment of untransformed cells is correlated with a decrease in cell cAMP levels and can be prevented by dibutyryl cAMP. The changed growth characteristics of transformed cells are discussed with regard to cAMP levels. 相似文献
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C Torda 《Biochimica et biophysica acta》1972,286(2):389-395
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Darren P. Wallace 《生物化学与生物物理学报:疾病的分子基础》2011,1812(10):1291-1300
In polycystic kidney disease (PKD), intracellular cAMP promotes cyst enlargement by stimulating mural epithelial cell proliferation and transepithelial fluid secretion. The proliferative effect of cAMP in PKD is unique in that cAMP is anti-mitogenic in normal renal epithelial cells. This phenotypic difference in the proliferative response to cAMP appears to involve cross-talk between cAMP and Ca2+ signaling to B-Raf, a kinase upstream of the MEK/ERK pathway. In normal cells, B-Raf is repressed by Akt (protein kinase B), a Ca2+-dependent kinase, preventing cAMP activation of ERK and cell proliferation. In PKD cells, disruption of intracellular Ca2+ homeostasis due to mutations in the PKD genes relieves Akt inhibition of B-Raf, allowing cAMP stimulation of B-Raf, ERK and cell proliferation. Fluid secretion by cystic cells is driven by cAMP-dependent transepithelial Cl− secretion involving apical cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channels. This review summarizes the current knowledge of cAMP-dependent cyst expansion, focusing on cell proliferation and Cl−-dependent fluid secretion, and discusses potential therapeutic approaches to inhibit renal cAMP production and its downstream effects on cyst enlargement. This article is part of a Special Issue entitled: Polycystic Kidney Disease. 相似文献
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Cyclic AMP in Metobolism 总被引:7,自引:0,他引:7
Throughout the animal kingdom cyclic AMP is involved in the regulation of enzyme activity under the influence of hormones. As this review shows, a few clues are beginning to emerge about the way in which this is being achieved. 相似文献
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Sparey T Beher D Best J Biba M Castro JL Clarke E Hannam J Harrison T Lewis H Madin A Shearman M Sohal B Tsou N Welch C Wrigley J 《Bioorganic & medicinal chemistry letters》2005,15(19):4212-4216
A novel series of N-alkyl-substituted cyclic sulfamides were developed from a screening hit. Chemistries were developed which allowed surveys of N-alkyl groups and amines resulting in the identification of N-trifluoroethyl-substituted cyclic sulfamides with good in vitro and in vivo gamma-secretase activity. One compound with subnanomolar activity elicited a reduction in brain Abeta40 after oral dosing in APP-YAC mice. 相似文献
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《Mathematical biosciences》1987,87(1):47-61
The theory of feedback control as a possible stabilizing mechanism has already been introduced into ecosystem analysis. One problem in the theory is the identification of the informational links by which such controls operate. Cyclic controls—for example, zero- mean sine functions added to certain exchange flows in the system—might also contribute to system stability. Their advantage is that they operate without need for information from the rest of the system. The theory of ecosystem cyclic control is presented and applied to data from an oyster reef ecosystem. 相似文献