Comparison of K,MgATPases in purified plasmalemma from wheat and oat. – Substrate specificities and effects of pH, temperature and inhibitors

Sommarin, Marianne; Lundborg, Tomas; Kylin, Anders

doi:10.1111/j.1399-3054.1985.tb02354.x

Cited by 70 publications

(44 citation statements)

References 13 publications

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“…ATPase activities were determined by measuring Pi hydrolysed from ATP over a 30 min period at 37 °C according to Sommarin, Lundborg & Kylin (1985) with minor modifications. The 0*5 ml reaction medium consisted of 0-25 M sucrose, 50 mM morpholinoethanesulphonic acid (MES)-KOH, pH 6-8, 0-05 % (v/w) Brij 58, 3 mM MgCla and 3 mM ATP.…”

Section: Enzyme Assaysmentioning

confidence: 99%

Physiological effects of copper on iron acquisition processes in Plantago

et al. 1997

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(This paper is dedicated to the memory of Professor Horst Marschner) SUMMARY In Plantago lanceolata L. the effect of Cu(II) additions to the nutrient solution on root-associated Fe(III) reductase was studied in a factorial design with different Cu(II) and Fe(III) concentrations. Iron starvation resulted in approx. an eightfold increase in root Fe reduction at the level of intact plants and twofold enhancement in the specific activity of both NADH-linked FeEDTA reductase and H^-ATPase in isolated root plasma membrane vesicles. In plants exposed to low (0-3-0-7 /iM) Cu and suboptimal Fe levels, reduction activity at the root surface was further increased and associated with more severe interveinal chlorosis than plants grown in Cufree medium. In Fe-sufficient plants, withholding Cu over a prolonged period slightly enhanced the reduction activity.Addition of high (5 fiM) Cu concentrations to Fe-free medium inhibited the induction of the physiological responses by Fe-deficiency stress. In plants without Fe supply but with adequate Cu supply, short-term application of 5 /iM CuSO^ completely inhibited the reduction activity. Neither incubation of the plasma membrane vesicles before measurement nor incubation of intact plants with Cu before isolation caused a significant decrease in reductase activity. The results are interpreted as indicating different mechanisms underlying Cu-induced alterations in iron nutrition.

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Section: Enzyme Assaysmentioning

confidence: 99%

Physiological effects of copper on iron acquisition processes in Plantago

et al. 1997

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“…Highly purified plasma membranes were isolated from the microsomal fraction (10,000-30,000g pellet) of wheat shoots and roots by partitioning in aqueous polymer two-phase systems as described earlier (28) with minor modifications (22 (11,19,21). As when isolating the original plasma membrane fraction, the rightside-out vesicles partitioned to the upper phase.…”

Section: Preparation Of Plasma Membranesmentioning

confidence: 99%

“…Wheat seedlings (Triticum aestivum L. cv Drabant) were grown hydroponically in the dark for 8 d (28).…”

Section: Plant Materialsmentioning

confidence: 99%

Polyphosphoinositide Phospholipase C in Plasma Membranes of Wheat (Triticum aestivum L.)

Pical

Sandelius²,

Melin³

et al. 1992

Plant Physiol.

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Polyphosphoinositide-specific phospholipase C activity was present in plasma membranes isolated from different tissues of several higher plants. Phospholipase C activities against added phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) were further characterized in plasma membrane fractions isolated from shoots and roots of dark-grown wheat (Triticum aestivum L. cv Drabant) seedlings. In right-side-out (70-80% apoplastic side out) plasma membrane vesicles, the activities were increased 3 to 5 times upon addition of 0.01 to 0.025% (w/ v) sodium deoxycholate, whereas in fractions enriched in insideout (70-80% cytoplasmic side out) vesicles, the activities were only slightly increased by detergent. Furthermore, the activities of inside-out vesicles in the absence of detergent were very close to those of right-side-out vesicles in the presence of optimal detergent concentration. This verifies the general assumption that polyphosphoinositide phospholipase C activity is located at the cytoplasmic surface of the plasma membrane. PIP and PIP2 phospholipase C was dependent on Ca21 with maximum activity at 10 to 100 Mm free Ca2 and half-maximal activation at 0.1 to 1 Mm free Ca2. In the presence of 10 gM Ca21, 1 to 2 mM MgCI2 or MgSO4 further stimulated the enzyme activity. The other divalent chloride salts tested (1.5 mm Ba2", Co2+, Cu2+, Mn2+, Ni2+, and Zn2+) inhibited the enzyme activity. The stimulatory effect by Mg2+ was observed also when 35 mm NaCI was included. Thus, the PIP and PIP2 phospholipase C exhibited maximum in vitro activity at physiologically relevant ion concentrations. The plant plasma membrane also possessed a phospholipase C activity against phosphatidylinositol that was 40 times lower than that observed with PIP or PIP2 as substrate. The phosphatidylinositol phospholipase C activity was dependent on Ca2 , with maximum activity at 1 mm CaC12, and could not be further stimulated by Mg2+.animal cells, phospholipase C-catalyzed production of the second messengers inositol 1,4,5-trisphosphate and diacylglycerol from PIP22 is a key event in the transduction of agonist-dependent signals over the plasma membrane (1,3,15). PIP2 is formed by a two-step phosphorylation of PI by PI kinase and PIP kinase, enzymes that are also present in plant plasma membranes (18,24,29). Because phospholipase C, preferentially active on PIP and PIP2, has also been identified in plasma membranes from plants (7,17,30), there is an enzymic basis for signal transduction through hydrolysis of polyphosphoinositides. However, very little is known about the mechanism operating in the plant plasma membrane, in part due to the scant knowledge about phospholipase C.In this communication, we present evidence for the localization of polyphosphoinositide phospholipase C activity in wheat (Triticum aestivum L. cv Drabant) plasma membranes to the cytoplasmic surface of the membrane. We also present a further characterization of the in vitro properties of the enzyme activity. MATERIALS AND METHODS

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“…Although differences in IDPase activity were evident between membrane fractions from leaves and tubers, activity increases were negligible over the 3-d incubation period at 4°C, reflecting an absence of latency and, thus, minimal contamination by Golgi vesicles. The pH optimum for enzyme activity was about 6.5, well within the range (pH 6.0-7.0) reported for plant PM ATPases (Sommarin et al, 1985;Sze, 1985;Palmgren and Sommarin, 1989). …”

Section: Characterization Of Pmsmentioning

confidence: 78%

Oxidative Stress Results in Increased Sinks for Metabolic Energy during Aging and Sprouting of Potato Seed-Tubers

Kumar

Knowles

1996

Plant Physiology

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Glutathione-mediated free-radical-scavenging and plasma membrane ATPase activities increase as sinks for metabolic energy with advancing tuber age. Plasma membrane ATPase activity from 19-month-old tubers was 77% higher than that from 7-month-old tubers throughout sprouting. The higher activity was not attended by an increase in the amount of ATPase per unit plasma membrane protein.Concentrations of oxidized (CSSC) and reduced glutathione more than doubled as tuber age advanced from 6 to 30 months, but the proportion of GSSG to total glutathione remained constant with age. l h e activity of glutathione transferase, an enzyme that catabolizes lipidhydroperoxides, increased by 44 and 205% on a fresh weight and protein basis, respectively, as tubers aged from 6 to 30 months. Glutathione reductase activity also increased with advancing age, by 90% on a fresh weight basis and 305% on a protein basis. Older tubers had more glutathione reductase per unit of soluble and mitochondrial protein. The age-induced increase in cytosolic glutathione transferase activity was likely due to increased availability of lipid-hydroperoxides and/or a positive effector. Synthesis of glutathione requires ATP, and the increased reduction of CSSC resulting from catalysis of lipidhydroperoxides is NADPH-dependent. Thus, increased plasma membrane ATPase and glutathione-mediated free-radical-scavenging activities likely constitute substantial sinks for ATP in older tubers prior to and during sprouting. lncreased oxidative stress and loss in membrane integrity are central features of aging that undoubtedly contribute to the enhanced respiration of sprouting older tubers.Potato (Solanum tuberosum L.) seed-tubers provide a model system for studies of the metabolic processes associated with aging of plant tissues in general and vegetative propagules in particular. Russet Burbank seed-tubers maintain their viability for about 3 years in cold storage (4"C, 95% RH); however, vigor and growth potential of tuber meristems depend on age. As tubers advance in age beyond about 7 months, apical dominance and plant vigor gradually decline, resulting in the production of many shoots per tuber, each with low specific leaf area and sparse root systems (Mikitzel and Knowles, 1990; Kumar and Knowles, 1993a). Paradoxically, older tubers have substantially higher rates of fully coupled, Cyt-mediated respiration than younger tubers at similar stages of sprout development (Kumar and Knowles, 1996). This greater ATP production by sprouting older tubers is required to '

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Comparison of K,MgATPases in purified plasmalemma from wheat and oat. – Substrate specificities and effects of pH, temperature and inhibitors

Cited by 70 publications

References 13 publications

Physiological effects of copper on iron acquisition processes in Plantago

Physiological effects of copper on iron acquisition processes in Plantago

Polyphosphoinositide Phospholipase C in Plasma Membranes of Wheat (Triticum aestivum L.)

Oxidative Stress Results in Increased Sinks for Metabolic Energy during Aging and Sprouting of Potato Seed-Tubers

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