Adenosine triphosphate receptor

Nucleotides acting at enzymes or receptor sites (e.g., adenosine triphosphate-receptors). 

Molybdate is also known as an inhibitor of the important enzyme ATP sulfurylase where ATP is adenosine triphosphate, which activates sulfate for participation in biosynthetic pathways (56). The tetrahedral molybdate dianion, MoO , substitutes for the tetrahedral sulfate dianion, SO , and leads to futile cycling of the enzyme and total inhibition of sulfate activation. Molybdate is also a co-effector in the receptor for steroids (qv) in mammalian systems, a biochemical finding that may also have physiological implications (57). 

Table 3. Agonists and Antagonists of Adenosine Triphosphate and Receptors...

FIGURE 3.11 Schematic representation of the transmembrane topology of the adenosine triphosphate (ATP) receptors. 

FIGURE 14-6 Main signaling pathways for histamine receptors. Histamine can couple to a variety of G-protein-linked signal transduction pathways via its four different receptors. The Hj receptor activates the phosphatidylinositol turnover via Gq/11 proteins. The other receptors either positively (H2 receptor) or negatively (H3 and H4 receptor) regulate adenylyl cyclase activity via Gs and GUo protein activation respectively. Several additional signaling pathways have been described, which are not shown. Abbreviations PfP2, phosphatidylinositol 4,5-bisphosphate PIC, phospholipase C AC, adenylyl cyclase ATP, adenosine triphosphate cAMP, cyclic AMP PKC, protein kinase C PICA, protein kinase A. 

ATP adenosine triphosphate GPCR G-protein coupled receptor... 

Figure 2.4. Relationship between the postsynaptic receptor and the secondary messenger system. GTP=guanosine triphosphate GDP=guanosine diphosphate ATP=adenosine triphosphate AMP=adenosine monophosphate.

The activation of adenylyl cyclase enables it to catalyze the conversion of adenosine triphosphate (ATP) to 3 5 -cyclic adenosine monophosphate (cAMP), which in turn can activate a number of enzymes known as kinases. Each kinase phosphorylates a specific protein or proteins. Such phosphorylation reactions are known to be involved in the opening of some calcium channels as well as in the activation of other enzymes. In this system, the receptor is in the membrane with its binding site on the outer surface. The G protein is totally within the membrane while the adenylyl cyclase is within the membrane but projects into the interior of the cell. The cAMP is generated within the cell (see Rgure 10.4). 

The role of cyclic 3, 5 -adenosine monophosphate (cAMP) as a second messenger in the actions of catecholamines acting on p-receptors. ATP adenosine triphosphate. 

Sympathetic arc involved in blood pressure regulation and sites where drugs may act to influence the system. A. Receptors on effector cell. 6. Adrenergic varicosity. C. Nicotinic receptors (postganglionic fibers). D. Brainstem nuclei. NTS, nucleus of the tractus solitarii VMC, vasomotor center ACh, acetylcholine NE, norepinephrine a, a-adrenoceptors (3, 13-adrenoceptors P2, P2-purinoceptors ATR adenosine triphosphate. 

The sulfonylurea receptor was identified as an adenosine triphosphate (ATP) sensitive potassium (Katp) channel that is present on the (3-cell membrane surface. Closure of these K tp channels causes (3-cell membrane... 

Schematic illustration of a generalized cholinergic junction (not to scale). Choline is transported into the presynaptic nerve terminal by a sodium-dependent choline transporter (CHT). This transporter can be inhibited by hemicholinium drugs. In the cytoplasm, acetylcholine is synthesized from choline and acetyl -A (AcCoA) by the enzyme choline acetyltransferase (ChAT). Acetylcholine is then transported into the storage vesicle by a second carrier, the vesicle-associated transporter (VAT), which can be inhibited by vesamicol. Peptides (P), adenosine triphosphate (ATP), and proteoglycan are also stored in the vesicle. Release of transmitter occurs when voltage-sensitive calcium channels in the terminal membrane are opened, allowing an influx of calcium. The resulting increase in intracellular calcium causes fusion of vesicles with the surface membrane and exocytotic expulsion of acetylcholine and cotransmitters into the junctional cleft (see text). This step can he blocked by botulinum toxin. Acetylcholine s action is terminated by metabolism by the enzyme acetylcholinesterase. Receptors on the presynaptic nerve ending modulate transmitter release. SNAPs, synaptosome-associated proteins VAMPs, vesicle-associated membrane proteins.

The development of anion coordination chemistry and anion receptor molecules has opened up the possibility to perform molecular catalysis on anionic substrates of chemical and biochemical interest, such as adenosine triphosphate. The catalysis of phosphoryl transfer is of particular interest, namely in view of the crucial role of such processes in biology and of the numerous enzymes that catalyse them. 

Fig. 9.1 Schematic diagram illustrating A3 adenosine receptor localization in the brain. ADO adenosine ADA adenosine deaminase ATP adenosine triphosphate, AMP adenosine mono-phospate AKA adenosine kinase T bidirezional nucleoside transporter NPTDase family of ecto-nucleotidases, including NPTDase 1,2,3. During cerebral ischemia, extracellular ADO concentration increases acting on A3 adenosine receptors located on different cell type...

Reeves JJ, Jones CA, Sheehan MJ, Vardey CJ, Whelan CJ (1997) Adenosine A3 receptors promote degranulation of rat mast cells both in vitro and in vivo. Inflamm Res 46(5) 180-184 Ribeiro JA, Walker J (1975) The effects of adenosine triphosphate and adenosine diphosphate on transmission at the rat and frog neuromuscular junctions. Br J Pharmacol 54(2) 213-218 Ribeiro JA, Sebastiao AM (1984) Enhancement of tetrodotoxin-induced axonal blockade by adenosine, adenosine analogues, dibutyryl cyclic AMP and methylxanthines in the frog sciatic nerve. Br J Pharmacol 83(2) 485—492... 

FIGURE 52.4 The insulin receptor. ATP = adenosine triphosphate ADP = adenosine diphosphate TYR = tyrosine. 

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