Triphosphatase

Contraction of muscle follows an increase of Ca " in the muscle cell as a result of nerve stimulation. This initiates processes which cause the proteins myosin and actin to be drawn together making the cell shorter and thicker. The return of the Ca " to its storage site, the sarcoplasmic reticulum, by an active pump mechanism allows the contracted muscle to relax (27). Calcium ion, also a factor in the release of acetylcholine on stimulation of nerve cells, influences the permeabiUty of cell membranes activates enzymes, such as adenosine triphosphatase (ATPase), Hpase, and some proteolytic enzymes and facihtates intestinal absorption of vitamin B 2 [68-19-9] (28). 

Mitchell, P., and Moyle, J., 1965. Stoichiometry of proton translocation through the re.spiratory chain and adeno.sine triphosphatase. systems of rat mitochondria. Nature 208 147-151. 

Na+/K+-ATPase sodium pump Sodium- and potassium-activated adenosine 5 -triphosphatase EC 3.6.1.37. 

Eisenberg, E. Moos, C. (1970). Actin activation of heavy-meromyosin adenosine triphosphatase. J. Biol. Chem. 245,2451-2456. 

Stein, L.A., Schwarz, R., Chock, P.B., Eisenberg, E. (1979). Mechanism of actomyosin adenosine triphosphatase. Evidence that adenosine 5 -triphosphate hydrolysis can occur without dissociation of the actomyosin complex. Biochemistry 18, 3895-3909. 

Trentham, D.R., Bardsley, R.G., Eccleston, J.F., Weeds, G. (1972). Elementary processes of the magnesium ion-dependent adenosine triphosphatase activity of heavy meromyosin. Biochem. J. 126, 635-644. 

Basha PM, Nayeemunnisa. 1993a. Effect of methyl parathion on Na, K, and Mg adenosine triphosphatase activity in developing central nervous system in rats. Indian J Exp Biol 31 785-787. 

AP = alkaline phosphatase ATPase = adenosine triphosphatase Cardio = cardiovascular d = day(s) Endocr = endocrine F = female Gastro = gastrointestinal Gn pig = guinea pig GOT = glutamic-oxaloacetic transaminase GPT = glutamic-pyruvic transaminase Hemato = hematological hr = hour(s) LDH = lactate dehydrogenase LOAEL = lowest-observable-adverse-effect level M = male Musc/skel = musculoskeletal NOAEL = no-observable-adverse-effect level ... 

Adenosine triphosphatase 4 Highly reactive compounds multitarget... 

Uptake of noradrenaline into the vesicles depends on an electrochemical gradient driven by an excess of protons inside the vesicle core. This gradient is maintained by an ATP-dependent vesicular H+-triphosphatase. Uptake of one molecule of noradrenaline into the vesicle by the transporter is balanced by the counter-transport of two H+ ions (reviewed by Schuldiner 1998). It is thought that either binding or translocation of one H+ ion increases the affinity of the transporter for noradrenaline and that binding of the second H+ actually triggers its translocation. 

Reserpine irreversibly inhibits the triphosphatase that maintains the proton gradient and so it depletes neurons of their vesicular store of transmitter. This explains why restoration of normal neuronal function rests on delivery of new vesicles from the cell bodies. Some amphetamine derivatives, including methylenedioxymethamphetamine (MDMA), are also substrates for the transporter and, as a result, competitively inhibit noradrenaline uptake. Another way of inhibiting the transporter is by dissipation of the pH gradient across the vesicular membrane i-chloroamphetamine is thought to act in this way. 

Harris, W.E. and Stahl, W.L. (1980). Oiganisation of thiol groups of electric eel electric organ Na/K ion stimulated adenosine triphosphatase, studied with bifunctional reagents. Biochem. J. 185, 787-790. 

ATHERO-ELAM A montxyte adhesion molecule ATL Adult T cell leukaemia ATP Adenosine triphosphate ATPase Adenosine triphosphatase ATP-ys Adenosine 3 thiotriphosphate AITP Autoimmune thrombcKytopenic purpura AUC Area under curve AVP Arginine vasopressin... 

GTPase Guanidine triphosphatase GVHD Graft-versus-host-disease GVHR Graft-versus-host-reaction... 

T. K. Hodges, R, T. Leonard, C. E, Bracker, and T. W. Keenan, Purification of an ion-stimulated adenosine triphosphatase from plant roots association with plasma membranes. Proc. Nat. Acad. Sci. U.S.A. 69 3307 (1972). 

The ventricular action potential is depicted in Fig. 6-2.2 Myocyte resting membrane potential is usually -70 to -90 mV, due to the action of the sodium-potassium adenosine triphosphatase (ATPase) pump, which maintains relatively high extracellular sodium concentrations and relatively low extracellular potassium concentrations. During each action potential cycle, the potential of the membrane increases to a threshold potential, usually -60 to -80 mV. When the membrane potential reaches this threshold, the fast sodium channels open, allowing sodium ions to rapidly enter the cell. This rapid influx of positive ions... 

Bragg, P.D., and Hou, C. (1975) Subunit composition, function, and spatial arrangement in the Ca2+-and Mg2+-activated adenosine triphosphatases of Escherichia coli and Salmonella typhimurium. Arch. Biochem. Biophys. 167, 311-321. 

Hiratsuka, T. (1987) Nucleotide-induced change in the interaction between the 20- and 26-kilodalton heavy-chain segments of myosin adenosine triphosphatase revealed by chemical cross-linking via the reactive thiol SH2. Biochemistry 26, 3168. 

Hiratsuka, T. (1988) Cross-linking of three heavy-chain domains of myosin adenosine triphosphatase with a trifunctional alkylating agent. Biochemistry 27, 4110. 

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