Nucleotide cyclases

Adenylyl cyclases belong to the larger class of purine nucleotide cyclases. These have been divided into classes I-VI [2]. Class I cyclases include those in gram negative bacteria, e.g. Escherichia coli and Yersinia pestis, in which cAMP levels respond to external... 

Nucleotide Cyclases. Calmodulin regulates the activity of different nucleotide cyclases such as adenylyl cyclase that catalyzes the formation of cAMP from ATP. cAMP is another important molecule in the cell functioning as a second-messenger like calcium. The cahnodulin-adenylyl cyclase interaction links these two second messengers together. ... 

Adenylyl Cyclases. Figure 6 Adenylyl cyclase catalytic cycle. Points during the catalytic cycle of adenylyl cyclases at which inhibition by competitive and noncompetitive nucleotides occur E represents the catalytic transition state. 

Adenylyl Cyclases. Table 4 Nucleotide inhibitors of adenylyl cyclase. Enzyme source and assay conditions were as for Table 3. Values obtained for 3 -ATP are overestimations due to the formation of 2 3 -cAMP from 3 -ATP that occurs nonenzymatically in the presence of divalent cation... 

Synthesized by soluble guanylyl cyclase and particulate guanylyl cyclase from guanosine triphosphate (GTP). Nitric oxide activates soluble guanylyl cyclase to enhance cyclic GMP production that contributes to various NO actions. Cyclic GMP is hydrolyzed by phosphodiesterases. Cyclic GMP binds to and activates cGMP-dependent protein kinase, phosphodiesterases, and Cyclic Nucleotide-regulated Cation Channels. 

Adenylyl Cyclases Guanylyl Cyclases Transmembrane Signalling Cyclic Adenosine Monophosphate Cyclic Guanosine Monophosphate Cyclic Nucleotide-gated Channels Phosphodiesterases... 

PDE1C2 and PDE4A are expressed. PDE1C2 is found in the cilia of the epithelium, where it colocalizes with adenylyl cyclase. PDE4A is found throughout the epithelial layer, but not in cilia. Therefore, as in the kidney mesangial cells, different PDEs must be working on different cyclic nucleotide pools. More recently, substantial data has been developed for compartmenta-tion of cAMP and PDEs in cardiac myocytes. 

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