ATP-activity

Shimomura, O. (1981). A new type of ATP-activated bioluminescent system in the millipede Luminodesmus sequoiae. FEBS Lett. 128 242-244. 

Several different types of photoprotein are presently known, for example the Ca2+-sensitive types found in various coelenter-ates (aequorin, obelin, mnemiopsin) and protozoa (thalassicolin) the peroxide-activation types found in scaleworm (polynoidin) and the clam Pholas (pholasin) and the ATP-activation type found in a Sequoia millipede Luminodesmus. 

FIGURE 57-6 Central sensitization of dorsal horn neurons and a loss of inhibition after nerve injury result in altered processing of sensory input. ATP activates microglia through the P2X4 receptor. The resulting release of cytokines contributes to the development of pain through a mechanism of action that is, as yet, unknown. 

Bean, B.P. ATP-activated channels in rat and bullfrog sensory neurons concentration dependence and kinetics, J. Neurosci. 1990, 10, 1-10. 

Ueno, S., Tsuda, M., Iwanga, T., Inoue, K. Cell-type specific ATP-activated responses in the rat dorsal root ganglion neurons, Br. J. Pharmacol. 1999, 126, 429-436. 

The coenzymatic function of biotin appears to be to mediate the carboxylation of substrates by accepting the ATP-activated carboxyl group and transferring it to the carboxyl acceptor substrate. There is good reason to believe that the enzymatic sites of ATP-dependent carboxylation of biotin are physically separated from the sites at which N -carboxybiotin transfers the carboxyl group to acceptor substrates, that is, the transcarboxylase sites. In fact, in the case of the acetyl-CoA carboxylase from E. coli (see chapter 18), these two sites reside on two different subunits, while the biotinyl group is bonded to a third, a small subunit designated biotin carboxyl carrier protein. 

The manner in which the reduction of ribonucleotides to deoxyribonucleotides is regulated has been studied with reductases from relatively few species. The enzymes from E. coli and from Novikoff s rat liver tumor have a complex pattern of inhibition and activation (fig. 23.25). ATP activates the reduction of both CDP and UDP. As dTTP is formed by metabolism of both dCDP and dUDP, it activates GDP reduction, and as dGTP accumulates, it activates ADP reduction. Finally, accumulation of dATP causes inhibition of the reduction of all substrates. This regulation is reinforced by dGTP inhibition of the reduction of GDP, UDP, and CDP and by dTTP inhibition of the reduction of the pyrimidine substrates. Because evidence suggests that ribonucleotide reductase may be the rate-limiting step in deoxyribonucleotide synthesis in at least some animal cells, these allosteric effects may be important in controlling deoxyribonucleotide synthesis. 

Shkorbatov, G.L., Gubin, I.E. and Dmitrenko, V.F. (1972). The oxidative and ATP-activity of carp muscle mitochondria as related to temperature adaptation (In Russian). In Energy Aspects of Growth and Metabolism of Aquatic Animals (G.E. Shulman, ed.), pp. 254-255. 

Nakatsuka T, Gu JG (2001) ATP P2X Receptor-mediated enhancement of glutamate release and evoked EPSCs in dorsal horn neurons of the rat spinal cord. J Neurosci 21 6522-31 Nakazawa K (1994) ATP-activated current and its interaction with acetylcholine-activated current in rat sympathetic neurons. J Neurosci 14 740-50 Narkiewicz K, van de Borne PJ, Hausberg M, Cooley RL, Winniford MD, Davison DE, Somers VK (1998) Cigarette smoking increases sympathetic outflow in humans. Circulation 98 528-34 Nicoll RA, Schmitz D (2005) Synaptic plasticity at hippocampal mossy fibre synapses. Nat Rev Neurosci 6 863-76... 

A fourth pattern of interaction (enzymes of group D) between allosteric activator and inhibitor is seen with barley endosperm. The ADPGIc PPase, which is poorly-activated by 3PGA, is inhibited by Pi (Table 4.2). However, 3PGA lowers (up to 3-fold) the S0 5 for ATP (i.e. the apparent affinity of ATP is increased) and the Hill coefficient.75 At 0.1 mM ATP, activation by 3PGA is about 4-fold 2.5 mM Pi reverses the effect. Thus, in barley endosperm, the prime effect of 3PGA or Pi may be to either increase or decrease the apparent affinity of the enzyme for the substrate, ATP. 

Sulfonium salts are common alkylating agents in biological systems. For example, ATP activation of methionine forms the sulfonium salt S-adenosyl methionine (SAM), a biological methylating agent. 

P2X purine nucleotide receptors (Na+, Ca2+ channel) ATP Activation of nerve transmission in brain... 

The chemical messenger alters the conformational state of an integral membrane protein that operates as a channel for the movement of ions (e.g., Na+, K+, Ca2+, Cl") across the plasma membrane. Excitatory neurotransmitters such as glutamate, acetylcholine and ATP activate ligandgated ion channels that promote the entry of Na+ and Ca2+ ions to depolarize (activate) neurones. The inhibitory neurotransmitter -y-aminobutyrate (GABA), on the other hand, promotes the entry of Cl- ions that hyperpolarize (deactivate) neurons. 

ATP Active metabolism Sensitive and representative for both oxidative phosphorylation and for glycolysis... 

Almost all cells have an active transport system to maintain nonequilibrium concentration levels of substrates. For example, in the mitochondrion, hydrogen ions are pumped into the intermembrane space of the organelle as part of producing ATP. Active transport concentrates ions, minerals, and nutrients inside the cell that are in low concentration... 

In the case of active transport, the movement of the substrate is coupled to some other energetic process AGpump), such as cotransport of another substrate or ion according to its electrochemical potential gradient or the hydrolysis of ATP. Active transport is generally considered to involve specifically coupled... 

Mutations in ATPS (sulfate adenylyl transferase, EC 2.7.7.4) in the yeast Schizosaccharomyces pombe resulted in increased selenate tolerance [207]. The selenate resistant phenotype of these mutants was correlated with low sulfate uptake capacity and low ATPS activity. 

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