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)

To adapt to environmental changes, plant cells very likely possess a biochemical system, using vacuoles, for maintaining cytoplasmic pH homeostasis. A simple approach is to estimate the active H(+) influx and H(+) efflux of isolated vacuolar vesicles, although there is no good mathematical model to describe H(+) flux. To establish a new quantitative model, vacuolar vesicles were isolated from hypocotyls of mung bean (Vigna radiata L.), and pyrophosphate (PPi)- or ATP-dependent acidification was monitored using acridine orange. The change of pH inside the vesicles (pH(in)) was calculated using a pH calibration curve relating fluorescence quenching with DeltapH. After formation of a steady state DeltapH, passive H(+) efflux was monitored after terminating pumping with ethylenediaminetetraacetate, and the relative H(+) permeability coefficient (p(H+)) was calculated. The H(+) efflux simulated using the p(H+) corresponded to the H(+) efflux determined experimentally. H(+) influx was then calculated by subtracting the predicted H(+) efflux from the experimental net H(+) influx. H(+) influx into vesicles driven by H(+)-PPase or H(+)-ATPase decreased exponentially as the intravesicular pH(in) decreased, suggesting modulation of pumping by DeltapH, pH(in), or both. Finally, the PPi- or ATP-dependent H(+) accumulation determined experimentally was closely simulated by the predicted H(+) influx and H(+) efflux. The ability to predict H(+) flux under different conditions provides a powerful tool for studying pH homeostasis.
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PMID:Improved mathematical model for estimating H+ influx and H+ efflux in plant vacuolar vesicles acidified by ATPase or pyrophosphatase. 1771 54

The time-dependent effect of 50mM NaCl on the activities of two tonoplast proton pumps was investigated in Cucumis sativus L. var. Krak root cells. Distinct activity profiles for vacuolar proton transporting ATPase (V-ATPase) (EC 3.6.3.14) and vacuolar proton transporting pyrophosphatase (V-PPase) (EC 3.6.1.1) under salinity are presented. ATP-dependent proton transport and ATP hydrolysis increased after 24h of NaCl exposure, and then decreased in roots stressed with NaCl for 4 and 8d. Both PP(i)-driven H(+) transport and PP(i) hydrolysis were clearly inhibited by NaCl at all times examined. It was demonstrated that changes in enzyme activities were not due to the salt action on the expression of encoding genes. The levels of specific transcripts for subunit A of V-ATPase (CsVHA-A), subunit c of V-ATPase (CsVHA-c) and V-PPase (CsVP) were similar in cucumber roots untreated (control) and treated with salt. Such results suggest that alterations of proton pump activities under salinity are rather due to the post-translational alterations induced by NaCl.
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PMID:Modification of vacuolar proton pumps in cucumber roots under salt stress. 1834 86

Roots undergo multiple changes as a consequence of arbuscular mycorrhizal (AM) interactions. One of the major alterations expected is the induction of membrane transport systems, including proton pumps. In this work, we investigated the changes in the activities of vacuolar and plasma membrane (PM) H(+) pumps from maize roots (Zea mays L.) in response to colonization by two species of AM fungi, Gigaspora margarita and Glomus clarum. Both the vacuolar and PM H(+)-ATPase activities were inhibited, while a concomitant strong stimulation of the vacuolar H(+)-PPase was found in the early stages of root colonization by G. clarum (30 days after inoculation), localized in the younger root regions. In contrast, roots colonized by G. margarita exhibited only stimulation of these enzymatic activities, suggesting a species-specific phenomenon. However, when the root surface H(+) effluxes were recorded using a noninvasive vibrating probe technique, a striking activation of the PM H(+)-ATPases was revealed specifically in the elongation zone of roots colonized with G. clarum. The data provide evidences for a coordinated regulation of the H(+) pumps, which depicts a mechanism underlying an activation of the root H(+)-PPase activity as an adaptative response to the energetic changes faced by the host root during the early stages of the AM interaction.
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PMID:Arbuscular mycorrhizal fungi induce differential activation of the plasma membrane and vacuolar H+ pumps in maize roots. 1884 97

Activities of the tonoplast ATPase (V-ATPase EC 3.6.1.3) and PPase (V-PPase EC 3.6.1.1) provide the proton gradient driving the accumulation of various metabolites, organic and inorganic ions in the plant vacuole. We used anion exchange chromatography, liquid-phase isoelectric focusing (IEF), and continuous-elution native polyacrylamide gel electrophoresis (preparative PAGE) to enrich the V-PPase from solubilized tonoplast proteins from suspension cultured cells of Chenopodium rubrum L.The fractions were identified by their enzymatic activity, sensitivity towards the specific PPase inhibitor aminomethylenediphosphonate, apparent molecular weight, and immunological reactivity with an antibody raised against mung bean V-PPase. All these different methods used for the separation of solubilized tonoplast proteins revealed the existence of two physically separable V-PPase proteins exhibiting substrate specific enzymatic activity and 66 kDa apparent molecular weight after sodium dodecyl sulfate(SDS)-PAGE. The isoelectric points of the active V-PPase forms were 5.05 and 5.48 (V-ATPase 6.1). On the basis of the observation of high recoveries of enzymatic activity after different preparations we suggest that the V-PPase proteins separated may represent physiologically occurring forms of the enzyme which cannot be distinguished by SDS-PAGE and Western blot.
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PMID:Heterogeneity of the vacuolar pyrophosphatase protein from Chenopodium rubrum. 1898 95

The efficient exclusion of excess Na from the cytoplasm and vacuolar Na(+) accumulation are the main mechanisms for the adaptation of plants to salt stress. This is typically carried out by transmembrane transport proteins that exclude Na(+) from the cytosol in exchange for H(+), a secondary transport process which is energy-dependent and driven by the proton-motive force generated by plasma-membrane and tonoplast proton pumps. Tonoplast enriched-vesicles from control and 150 mM NaCl-tolerant calli lines were used as a model system to study the activity of V-H(+)-PPase and V-H(+)-ATPase and the involvement of Na(+) compartmentalization into the vacuole as a mechanism of salt tolerance in Solanum tuberosum. Both ATP- and pyrophosphate (PP(i))-dependent H(+)-transport were higher in tonoplast vesicles from the salt-tolerant line than in vesicles from control cells. Western blotting of tonoplast proteins confirmed that changes in V-H(+)-PPase activity are correlated with increased protein amount. Conversely, immunodetection of the A-subunit of V-H(+)-ATPase revealed that a mechanism of post-translational regulation is probably involved. Na(+)-dependent dissipation of a pre-established pH gradient was used to measure Na(+)/H(+) exchange in tonoplast vesicles. The initial rates of proton efflux followed Michaelis-Menten kinetics and the V(max) of proton dissipation was 2-fold higher in NaCl-tolerant calli when compared to the control. H(+)-coupled exchange was specific for Na(+) and Li(+) and not for K(+). The increase of both the pH gradient across the tonoplast and the Na(+)/H(+) antiport activity in response to salt strongly suggests that Na(+) sequestration into the vacuole contributes to salt tolerance in potato.
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PMID:Activity of tonoplast proton pumps and Na+/H+ exchange in potato cell cultures is modulated by salt. 1921 10

Acidocalcisomes are acidic organelles with a high concentration of phosphorus present as pyrophosphate (PP(i)) and polyphosphate (poly P) complexed with calcium and other cations. The acidocalcisome membrane contains a number of pumps (Ca(2+)-ATPase, V-H(+)-ATPase, H(+)-PPase), exchangers (Na(+)/H(+), Ca(2+)/H(+)), and channels (aquaporins), while its matrix contains enzymes related to PP(i) and poly P metabolism. Acidocalcisomes have been observed in pathogenic, as well as non-pathogenic prokaryotes and eukaryotes, e.g. Chlamydomonas reinhardtii, and Dictyostelium discoideum. Some of the potential functions of the acidocalcisome are the storage of cations and phosphorus, the participation of phosphorus in PP(i) and poly P metabolism, calcium homeostasis, maintenance of intracellular pH homeostasis, and osmoregulation. In addition, acidocalcisomes resemble lysosome-related organelles (LRO) from mammalian cells in many of their properties. For example, we found that platelet dense granules, which are LROs, are very similar to acidocalcisomes. They share a similar size, acidic properties, and both contain PP(i), poly P, and calcium. Recent work that indicates that they also share the system for targeting of their membrane proteins through adaptor protein 3 reinforces this concept. The fact that acidocalcisomes interact with other organelles in parasitic protists, e.g. the contractile vacuole in Trypanosoma cruzi, and other vacuoles observed in Toxoplasma gondii, suggests that these cellular compartments may be associated with the endosomal/lysosomal pathway.
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PMID:The role of acidocalcisomes in parasitic protists. 1952 47

Acidocalcisomes are acidic electron-dense organelles, rich in polyphosphate (poly P) complexed with calcium and other cations. While its matrix contains enzymes related to poly P metabolism, the membrane of the acidocalcisomes has a number of pumps (Ca(2+)-ATPase, V-H(+)-ATPase, H(+)-PPase), exchangers (Na(+)/H(+), Ca(2+)/H(+)), and at least one channel (aquaporin). Acidocalcisomes are present in both prokaryotes and eukaryotes and are an important storage of cations and phosphorus. They also play an important role in osmoregulation and interact with the contractile vacuole complex in a number of eukaryotic microbes. Acidocalcisomes resemble lysosome-related organelles (LRO) from mammalian cells in many of their properties. They share similar morphological characteristics, acidic properties, phosphorus contents and a system for targeting of their membrane proteins through adaptor complex-3 (AP-3). Storage of phosphate and cations may represent the ancestral physiological function of acidocalcisomes, with cation and pH homeostasis and osmoregulatory functions derived following the divergence of prokaryotes and eukaryotes.
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PMID:Evolution of acidocalcisomes and their role in polyphosphate storage and osmoregulation in eukaryotic microbes. 2012 44

The productivity of higher plants as a major source of food and energy is linked to their ability to buffer changes in the concentrations of essential and toxic ions. Transport across the tonoplast is energized by two proton pumps, the vacuolar H(+)-ATPase (V-ATPase) and the vacuolar H(+)-pyrophosphatase (V-PPase); however, their functional relation and relative contributions to ion storage and detoxification are unclear. We have identified an Arabidopsis mutant in which energization of vacuolar transport solely relies on the activity of the V-PPase. The vha-a2 vha-a3 double mutant, which lacks the two tonoplast-localized isoforms of the membrane-integral V-ATPase subunit VHA-a, is viable but shows day-length-dependent growth retardation. Nitrate content is reduced whereas nitrate assimilation is increased in the vha-a2 vha-a3 mutant, indicating that vacuolar nitrate storage represents a major growth-limiting factor. Zinc is an essential micronutrient that is toxic at excess concentrations and is detoxified via a vacuolar Zn(2+)/H(+)-antiport system. Accordingly, the double mutant shows reduced zinc tolerance. In the same way the vacuolar Na(+)/H(+)-antiport system is assumed to be an important component of the system that removes sodium from the cytosol. Unexpectedly, salt tolerance and accumulation are not affected in the vha-a2 vha-a3 double mutant. In contrast, reduction of V-ATPase activity in the trans-Golgi network/early endosome (TGN/EE) leads to increased salt sensitivity. Taken together, our results show that during gametophyte and embryo development V-PPase activity at the tonoplast is sufficient whereas tonoplast V-ATPase activity is limiting for nutrient storage but not for sodium tolerance during vegetative and reproductive growth.
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PMID:Arabidopsis V-ATPase activity at the tonoplast is required for efficient nutrient storage but not for sodium accumulation. 2013 98

The activity and subunit amounts of V-ATPase and V-PPase in various plants of Butea monosperma Taub. (Fabaceae) (ver. Dhak; Palas) growing as a natural inhabitant in varying stress conditions in southeast Rajasthan were studied. Western blot analysis followed by immunological quantification of V-ATPase subunits using specific polyclonal antibodies showed that the subunits A, B, D, E, and c are clearly detectable in all plants, with A, B, and c appearing as intense bands. The other subunits of V-ATPase, viz., C, a, and d, were also detected in majority of the plants. Various subunits exhibited variations in their protein amount in different plants. Besides, a few other clear bands were also detected. Of these, the 30- and 29-kD bands may possibly be Di and Ei. Furthermore, a clear band of V-PPase corresponding to 67-70 kD was also detected. A comparison of the V-ATPase and V-PPase activity revealed that Butea plants in the upper region of the study site showed 70% and 39% higher activity, respectively. Furthermore, the immunological quantification showed that the V-ATPase and V-PPase protein amounts are also higher in the upper Butea plants which have drought stress and, moreover, are also exposed to stronger light intensities for relatively longer duration.
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PMID:Stress-mediated alteration in V-ATPase and V-PPase of Butea monosperma. 2057 71

Most plants have two types of H(+)-translocating inorganic pyrophosphatases (H(+)-PPases), I and II, which differ in primary sequence and K(+) dependence of enzyme function. Arabidopsis thaliana has three genes for H(+)-PPases: one for type I and two for type II. The type I H(+)-PPase requires K(+) for maximal enzyme activity and functions together with H(+)-ATPase in vacuolar membranes. The physiological role of the type II enzyme, which does not require K(+), is not clear. We focused on the type II enzymes (AtVHP2;1 and AtVHP2;2) of A. thaliana. Total amounts of AtVHP2s were quantified immunochemically using a specific antibody and determined to be 22 and 12 ng mg(-1) of total protein in the microsomal fractions of suspension-cultured cells and young roots, respectively, and the values are approximately 0.1 and 0.2%, respectively, of the vacuolar H(+)-PPase. In plants, AtVHP2s were detected immunochemically in all tissues except mature leaves, and were abundant in roots and flowers. The intracellular localization of AtVHP2s in suspension cells was determined by sucrose density gradient centrifugation and immunoblotting. Comparison with a number of marker proteins revealed localization in the Golgi apparatus and the trans-Golgi network. These results suggest that the type II H(+)-PPase functions as a proton pump in the Golgi and related vesicles in young tissues, although its content is very low compared with the type I enzyme.
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PMID:Quantification, organ-specific accumulation and intracellular localization of type II H(+)-pyrophosphatase in Arabidopsis thaliana. 2060 24


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