Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.14 (ATP synthase)
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Pneumocystis carinii is an opportunistic fungus which causes interstitial pneumonia in patients with acquired immunodeficiency syndrome (AIDS). Cytoplasmic pH (pHi) regulation in short-term-cultured P. carinii trophozoites was studied using the fluorescent dye 2',7'-bis-(2-carboxyethyl)-5-(-6)-carboxyfluorescein. With an extracellular pH of 7.4, the mean baseline pHi of P. carinii trophozoites was 7.40 +/- 0.10 (n = 8). This steady-state pHi was not significantly affected in the absence of extracellular Na+ or K+. Moreover, steady-state pHi was maintained in the nominal absence of HCO3- and was not affected by the Cl-/HCO(3-)-exchanger inhibitor 4, 4'-di-isothiocyanato-dihydrostilbene-2, 2'-disulphonic acid (100 microM), or the Na+/H(+)-exchanger inhibitor N-ethyl-N-isopropylamiloride (100 microM). In contrast, the general inhibitors of ATPases, N-ethylmaleimide (1 mM), and dicyclohexylcarbodi-imide (100 microM), and the inhibitor of yeast H(+)-ATPase, diethylstilbestrol (12.5-100 microM), decreased pHi, while the K+/H(+)-ATPase inhibitor omeprazole (50-400 microM), and the vacuolar-type H(+)-ATPase inhibitor bafilomycin A1 (1-5 microM) only produced a dose-dependent acidification of the cells when used at high concentrations. In addition, steady-state pHi depended on the availability of cellular ATP, since it was decreased by the ATP synthase inhibitors oligomycin (1 microgram/ml) and sodium azide (1 mM), and by the uncoupler of oxidative phosphorylation carbonyl cyanide p-trifluorophenylhydrazone (1 microM), agents that were able to deplete significantly the intracellular ATP levels. Taken together, these results are consistent with an important role of an H(+)-ATPase similar to those found in other fungi in the regulation of pHi homoeostasis in P. carinii trophozoites.
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PMID:An H(+)-ATPase regulates cytoplasmic pH in Pneumocystis carinii trophozoites. 868 17

Submitochondrial particles freshly prepared by sonication from pea cotyledon mitochondria showed low ATPase activity. Activity increased 20-fold on exposure to trypsin. The pea cotyledon submitochondrial particle ATPase was also activated by "aging" in vitro. At pH 7.0 addition of 1 millimolar ATP prevented the activation. ATPase of freshly prepared pea cotyledon submitochondrial particles had a substrate specificity similar to that of the soluble ATPase from pea cotyledon mitochondria, with GTPase > ATPase. "Aged" or trypsin-treated particles showed equal activity with the two substrates. NaCl and NaHCO(3), which stimulate the ATPase but not the GTPase activity of the soluble pea enzyme, were stimulatory to both the ATPase and GTPase activities of freshly prepared submitochondrial particles. However, they were stimulatory only to the ATPase activity of trypsin-treated or "aged" submitochondrial particles. In contrast, the ATPase activity of rat liver submitochondrial particles was stimulated by HCO(3) (-), but inhibited by Cl(-), indicating that Cl(-) stimulation is a distinguishing property of the pea mitochondrial ATPase complex.
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PMID:ATPase Activity of Pea Cotyledon Submitochondrial Particles: ACTIVATION, SUBSTRATE SPECIFICITY, AND ANION EFFECTS. 1666 Nov 74