Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies have shown that histochemical modifications of the endoplasmic reticulum in epithelial cells might be related to their transport function. We have examined the effect of sodium maleate, which produces generalized transport derangement reminiscent of Fanconi syndrome, on the organization, morphology and enzyme activities of endoplasmic reticulum in rat kidney cells. The osmium impregnation technique has revealed that apical vacuoles increase in volume and in number in most proximal tubule cells, and contain osmium deposits. Osmium impregnation of the endoplasmic reticulum is much reduced. In vitro studies, performed with isolated microsomes, show NADPH cytochrome c reductase activity in both normal and maleate-treated rats. As revealed by vanadate, Ca+-ATPase activity in isolated microsomes is unnaffected by maleate but the vanadate-insensitive or passive component of calcium uptake increases particularly later in the response. Therefore, the remaining calcium uptake in the presence of vanadate is indeed passive; in vivo maleate administration also appears to increase the passive entry of calcium into the microsomal compartment. The morphological and histochemical alterations of the endoplasmic reticulum cisternae occur rapidly and with a similar time course to the transport defects, suggesting that this organelle plays a role in transcellular transport. Maleate may directly affect the endoplasmic reticulum membranes whereby passive permeability to calcium is increased. The endocytotic apparatus and possibly exocytosis phenomena are modified by maleate as shown by the increased vacuolization and the presence of black osmium deposits in vacuoles.
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PMID:Maleate modifies apical endocytosis and permeability of endoplasmic reticulum membranes in kidney tubular cells. 858 57

A fraction containing plasma membrane-enriched vesicles has been prepared from Tritrichomonas foetus. Cells were ruptured using a Potter type homogenizer, under well controlled conditions, and membranes were isolated by differential centrifugation and in discontinuous sucrose gradient. This fraction was enriched 8 and 10-fold in the plasma membrane marker enzymes 5'-nucleotidase and (Na+ + K+)-dependent, ouabain-sensitive ATPase, respectively. Determination of Glucose-6-phosphatase and NADPH cytochrome c reductase activities in this fraction, indicates a minimal contamination with endoplasmic reticulum membranes. Analysis by Sodium Dodecyl Sulfate-Polyacrylamide (SDS-PAGE) gradient gel showed that the plasma membrane fraction contains several proteins with major bands corresponding to apparent molecular weights of 48, 45, 39, 37, 32, 30, 27, 23, 20, 19, 17, and 15 kDa.
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PMID:Isolation and biochemical characterization of the plasma membrane of Tritrichomonas foetus. 865 56

Thymi of adult chickens (White Leghorn strain), ages of 6, 18, 45, days and 1, 3, 6, months, were studied by histological and histochemical stainings, histoenzymatic reactions (LDH, SDH, alpha-GPDH, NADH, NADPH, Ca++ dependent ATPase, pH 8.5) and by anti-thymostimulin immunoreaction. Positive reactions for thymostimulin-like substance, mucopolysaccharides and enzymatic activities were located in different epithelial compartments of the cortical and medullary zones. In 3 and 6 month-old chickens, there was a progressive reduction of the cortical area and of the number of cortical and medullary epithelial cells, and, in the thymi of the 6 month-old chickens, a partial decline in the immunological reactivity to anti-TS, but the intensity of the histochemical and enzymatic reactivities, in comparison with the thymi of the youngest chickens, was not decreased. This may suggest that the cortical and medullary epithelial cells still present in these thymi are capable of secreting and expressing activities and, thus, may maintain their functions.
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PMID:Identification of cells secreting a thymostimulin-like substance and examination of some histoenzymatic pathways in aging avian primary lymphatic organs: I. thymus. 883 83

The PMR1 gene of Saccharomyces cerevisiae is thought to encode a putative Ca(2+)-ATPase [1]. Membranes isolated from wild-type cells and from pmr1 null mutant of S. cerevisiae were fractionated on sucrose density gradients. In the pmr1 mutant we found a decrease in activity of the P-type ATPase and of ATP-dependent, protonophore-insensitive Ca2+ transport in light membranes, that comigrate with the Golgi marker GDPase. We conclude that the product of the PMR1 gene (Pmr1p) is indeed a Ca(2+)-ATPase of the Golgi and Golgi-like membranes. Surprisingly, the pmr1 null mutation abolished Ca(2+)-ATPase activity in Golgi and/or Golgi-like membranes only to 50% under conditions where they are separated from vacuolar membranes. This indicates that an additional Ca(2+)-ATPase is localized in Golgi and/or Golgi-like membranes. Moreover, a third Ca(2+)-ATPase is found in the ER and ER-like membranes. The data are consistent with the assumption that these Ca(2+)-ATPases are encoded by gene(s) different from PMR1. Disruption of PMR1 Ca(2+)-ATPase causes significant redistribution of enzyme activities and of total protein in compartments of the secretory pathway. A decrease in activity is observed for three integral membrane proteins: NADPH cytochrome c reductase, dolichyl phosphate mannose synthase, and Ca(2+)-ATPase, and also for total protein in Golgi, Golgi-like compartments and in vacuoles, whereas a corresponding increase of these activities is observed in endoplasmic reticulum and endoplasmic reticulum-like membranes. We assume that Ca(2+)-ATPases and sufficient Ca2+ gradients across the organellar membranes are important for the correct sorting of proteins to the various compartments of the secretory apparatus.
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PMID:Ca(2+)-ATPases of Saccharomyces cerevisiae: diversity and possible role in protein sorting. 959 67

Isocitrate dehydrogenase (IDH)(1) of Escherichia coli is regulated by a bifunctional protein, IDH kinase/phosphatase. In this paper, we demonstrate that the effectors controlling these activities belong to two distinct classes that differ in mechanism and in the locations of their binding sites. NADPH and isocitrate are representative members of one of these effector classes. NADPH inhibits both IDH kinase and IDH phosphatase, whereas isocitrate inhibits only IDH kinase. Isocitrate can "activate" IDH phosphatase by reversing product inhibition by dephospho-IDH. Mutations in icd, which encodes IDH, had parallel effects on the binding of these ligands to the IDH active site and on their effects on IDH kinase and phosphatase, indicating that these ligands regulate IDH kinase/phosphatase through the IDH active site. Kinetic analyses suggested that isocitrate and NADPH prevent formation of the complex between IDH kinase/phosphatase and its protein substrate. AMP, 3-phosphoglycerate, and pyruvate represent a class of regulatory ligands that is distinct from that which includes isocitrate and NADPH. These ligands bind directly to IDH kinase/phosphatase, a conclusion which is supported by the observation that they inhibit the IDH-independent ATPase activity of this enzyme. These effector classes can also be distinguished by the observation that mutant derivatives of IDH kinase/phosphatase expressed from aceK3 and aceK4 exhibited dramatic changes in their responses to AMP, 3-phosphoglycerate, and pyruvate but not to NADPH and isocitrate.
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PMID:Locations of the regulatory sites for isocitrate dehydrogenase kinase/phosphatase. 1062 15

In guard cells, membrane hyperpolarization in response to a blue light (BL) stimulus is achieved by the activation of a plasma membrane H(+)-ATPase. Using the patch clamp technique on broad bean (Vicia faba) guard cells we demonstrate that both steady-state- and BL-induced pump currents require ATP and are blocked by vanadate perfused into the guard cell during patch clamp recording. Background-pump current and BL-activated currents are voltage independent over a wide range of membrane potentials. During BL-activated responses significant hyperpolarization is achieved that is sufficient to promote K(+) uptake. BL activation of pump current becomes desensitized by three or four pulses of 30 s x 100 micromol m(-2) s(-1) BL. This desensitization is not a result of pump inhibition as maximal responses to fusicoccin are observed after full BL desensitization. BL treatments prior to whole cell recording show that BL desensitization is not due to washout of a secondary messenger by whole cell perfusion, but appears to be an important feature of the BL-stimulated pump response. We found no evidence for an electrogenic BL-stimulated redox chain in the plasma membrane of guard cells as no steady-state- or BL-activated currents are detected with NADH or NADPH added to the cytosol in the absence of ATP. Steady-state- nor BL-activated currents are affected by the inclusion along with ATP of 1 mM NADH in the pipette under saturating red light or by including NADPH in the pipette under darkness or saturating red light. These data suggest that reduced products of photosynthesis do not significantly modulate plasma membrane pump currents and are unlikely to be critical regulators in BL-stimulation of the plasma membrane H(+)-ATPase in guard cells.
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PMID:Apparent absence of a redox requirement for blue light activation of pump current in broad bean guard cells. 1115 40

The thiourea insecticide/acaricide diafenthiuron represents a biologically inactive propesticide that requires transformation into the active carbodiimide derivative. The carbodiimide inhibits mitochondrial respiration by selective and covalent binding to the proteolipid (8 kDa) of Fo-ATPase in the inner membrane and to porin (30 kDa) in the outer membrane. The thiourea can be activated by light as well as by cytochrome P450 in the insect. To get insight into the enzymatic mechanisms of activation, model in vitro studies were performed using [14C]diafenthiuron and microsomes from various vertebrate livers and from locust Malpighian tubules. Though there was a common set of metabolites, their quantities varies significantly with the species and assay conditions. As a typical product, p-hydroxydiafenthiuron was identified in assay with rat and mouse microsomes. The sulfomonoxide predominated in hen and fish assays, whereas pig and bovine microsomes almost exclusively produced the carbodiimide. The sulfoxide was shown to be a precursor of the carbodiimide. Formation of all metabolites was dependent on the presence of NADPH and active microsomes. The effects of inhibitors and the requirement for NAPDH suggested a role of cytochrome P450-dependent monooxygenase(s) in the formation of both the hydroxylated product and the carbodiimide. FAD-dependent monooxygenases (FMOs) may also be involved in a step following sulfoxidation. These in vitro studies revealed potential mechanisms contributing to biological selectivity of the effects of a pesticide that acts in a non-selective mode at a conserved mitochondrial site.
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PMID:Metabolism of diafenthiuron by microsomal oxidation: procide activation and inactivation as mechanisms contributing to selectivity. 1169 92

The synthesis of the free radical gas nitric oxide (NO) is catalyzed by the enzyme NO synthase (NOS). NOS converts arginine and molecular oxygen to NO and citrulline in a reaction that requires NADPH, FAD, FMN, and tetrahydrobiopterin as cofactors. Three types of NOS have been identified by molecular cloning. The activity of the constitutively expressed neuronal NOS (nNOS) and endothelial NOS (eNOS) is Ca(2+)/calmodulin-dependent, whereas that the inducible NOS (iNOS) is Ca(2+)-insensitive. The predominant NOS isoform in skeletal muscle is nNOS. It is present at the sarcolemma of both extra- and intrafusal muscle fibers. An accentuated accumulation of nNOS is found in the endplate area. This strict sarcolemmal localization of nNOS is due its association with the dystrophin-glycoprotein complex, which is mediated by the syntrophins. The activity of nNOS in skeletal muscle is regulated by developmental, myogenic, and neurogenic influences. NO exerts several distinct effects on various aspects of skeletal muscle function, such as excitation-contraction coupling, mitochondrial energy production, glucose metabolism, and autoregulation of blood flow. Inside the striated muscle fibers, NO interacts directly with several classes of proteins, such as soluble guanylate cyclase, ryanodine receptor, sarcoplasmic reticulum Ca(2+)-ATPase, glyceraldehyde-3-phosphate dehydrogenase, and mitochondrial respiratory chain complexes, as well as radical oxygen species. In addition, NO produced and released by contracting muscle fibers diffuses to nearby arterioles where it acts to inhibit reflex sympathetic vasoconstriction.
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PMID:NO message from muscle. 1174 89

The metabolism of 1-(2-methyl-4-methoxyphenyl)-4-[(3-hydroxypropyl)amino]-6-methyl-2,3-dihydropyrrolo[3,2c]quinoline (DBM-819), a new H(+)/K(+) ATPase inhibitor, has been studied by HPLC with spectrometric detection and on-line LC-electrospray mass spectrometry. In vitro incubation of DBM-819 with rat liver microsomes in the presence of NADPH resulted in the production of four metabolites (M1-4), whereas DBM-819 was oxidized to two metabolites, M2 and M4, by human liver microsomes. M2, M3 and M4 were identified as O-demethyl-DBM-819, 8-hydroxy-DBM-819 and N-dehydroxypropyl-DBM-819, respectively, based on LC/MS/MS analysis with authentic standards. M1 was tentatively identified as 1-(hydroxy-2-methyl-4-methoxyphenyl)-4-[(3-hydroxypropyl)amino]-6-methyl-2,3-dihydropyrrolo[3,2c]quinoline. Rat liver CYP1A1/2 catalyzed the oxidation of DBM-819 to 8-hydroxy-DBM-819 and N-dehydroxypropyl-DBM-819. Human CYP3A4 was a major isozyme for the formation of O-demethyl-DBM-819 as well as N-dehydroxypropyl-DBM-819.
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PMID:In vitro metabolism of a new H(+)/K(+) ATPase inhibitor DBM-819 in liver microsomes using HPLC and electrospray mass spectrometry. 1174 83

Since Henze discovered vanadium in the blood (or coelomic) cells of an ascidian in 1911, this unusual phenomenon has attracted the interest of many investigators. The highest concentration of vanadium (350 mM) in the blood cells of Ascidia gemmata, which belongs to the suborder Phlebobranchia, is 10(7) times higher than that in seawater. Of the approximately 10 types of blood cells, a combination of cell fractionation and neutron-activation analysis revealed that the signet ring cells were the true vanadocytes. In the vanadocytes, 97.6% of the vanadium is in the +3 oxidation state (III). The extremely low pH of 1.9 found in vanadocytes suggests that protons, concentrated by an H(+)-ATPase, might be linked to the accumulation of vanadium energetically. The antigen recognized by a monoclonal antibody, S4D5, prepared to identify vanadocytes, was determined to be 6-PGDH in the pentose phosphate pathway. NADPH produced in the pentose phosphate pathway in vanadocytes is thought to participate in the reduction of vanadium(V) to vanadium(IV). During embryogenesis, a vanadocyte-specific antigen first appears in the body wall at the same time that significant accumulations of vanadium become apparent. Three different vanadium-associated proteins (VAPs) were extracted from the blood cells of vanadium-rich ascidians. These are 12.5, 15, and 16 kDa in size and are associated with vanadium in an approximate ratio of 1:16. The cDNA encoding the 12.5 and 15 kDa VAPs was isolated and the proteins encoded were found to be novel. Further biochemical and biophysical characterization of the VAPs is in progress.
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PMID:Vanadocytes, cells hold the key to resolving the highly selective accumulation and reduction of vanadium in ascidians. 1192 44


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