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PubMed1987

Divalent cation and hydrogen ion effects on the structure and surface activity of pulmonary surfactant.

The structure and surface activity of the extracellular fraction of pulmonary surfactant known as tubular myelin are Ca2+ dependent. Previous studies have demonstrated surfactant-specific proteins with monomeric molecular weights of 28,000-36,000 (SP28-36) are associated with this fraction. In reassembled lipoprotein mixtures, SP28-36 promotes the Ca2+-induced aggregation and surface activity of surfactant lipids, but the detailed interactions between Ca2+, SP28-36, and surfactant lipids have not been established. In this study, we investigated the effect of various cations on the aggregation of surfactant lipid liposomes in the presence of SP28-36. SP28-36 reduced the threshold ion concentration for liposome aggregation from greater than 10 to 0.5 mM for Ca2+, Ba2+, and Sr2+ but not Mg2+ or Mn2+. The liposome aggregation was reversed by ethylenediaminetetraacetic acid and not associated with leakage of carboxyfluorescein. SP28-36 promoted similar liposome aggregation at pH less than 5 in the absence of divalent cations. Surfactant lipids adsorbed slowly to an air-fluid interface in all ionic conditions unless SP28-36 was present. Both Ca2+ and H+ induced rapid lipid adsorption in the presence of SP28-36. The surface activity of native surfactant had a similar ion dependence. Electron micrographs of native surfactant showed typical tubular myelin structures at pH 7.4 only in the presence of Ca2+. At pH 4.4 in the absence of Ca2+, similar but not identical structures were seen. In the reconstituted system, SP28-36 in the presence of Ca2+ induced the formation of larger multilayered structures including parallel bilayers and small areas of squares and triangles with dimensions similar to structures found in the native material.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Tetramerisation of alpha-latrotoxin by divalent cations is responsible for toxin-induced non-vesicular release and contributes to the Ca(2+)-dependent vesicular exocytosis from synaptosomes.

A novel procedure of alpha-latrotoxin (alpha LTX) purification has been developed. Pure alpha LTX has been demonstrated to exist as a very stable homodimer. Such dimers further assemble into tetramers, and Ca(2+), Mg(2+) or higher toxin concentrations facilitate this process. However, when the venom is treated with EDTA, purified alpha LTX loses the ability to tetramerise spontaneously; the addition of Mg(2+) or Ca(2+) restores this ability. This suggests that alphaLTX has some intrinsically bound divalent cation(s) that normally support its tetramerisation. Single-particle cryoelectron microscopy and statistical image analysis have shown that: 1) the toxin has a non-compact, branching structure; 2) the alpha LTX dimers are asymmetric; and 3) the tetramers are symmetric and have a 25 A-diameter channel in the centre. Both alpha LTX oligomers bind to the same receptors in synaptosomes and rat brain sections. To study the effects of the dimers and tetramers on norepinephrine release from rat cerebrocortical synaptosomes, we used the EDTA-treated and untreated toxin preparations. The number of tetramers present in a preparation correlates with alpha LTX pore formation, suggesting that the tetramers are the pore-forming species of alpha LTX. The toxin actions mediated by the pore include: 1) Ca(2+) entry from the extracellular milieu; and 2) passive efflux of neurotransmitters via the pore that occurs independently of Ca(2+). The Ca(2+)-dependent alpha LTX-stimulated secretion conforms to all criteria of vesicular exocytosis but also depends upon intact intracellular Ca(2+) stores and functional phospholipase C (PLC). The Ca(2+)-dependent effect of the toxin is stronger when dimeric alpha LTX is used, indicating that higher receptor occupancy leads to its stronger activation, which contributes to stimulation of neuroexocytosis. In contrast, the Ca(2+)-independent release measured biochemically represents leakage of neurotransmitters through the toxin pore. These results are discussed in relation to the previously published observations.

Animals↗
PubMed1983

Stimulus-secretion coupling of glucose-induced insulin release. LI. Divalent cations and ATPase activity in pancreatic islets.

Pancreatic islets can be viewed as a fuel-sensor organ. The amount of ATP used by the islet cells for the maintenance of adequate Ca2+ gradients across membranes is not known. An indirect approach to this issue consists in the measurement of Ca-ATPase activity. The kinetics of Ca-ATPase in islet homogenates yielded a Km for ATP close to 0.1 mM and two Km values for Ca2+ close to 0.13 and 4-6 microM, respectively. Within limits, the Ca-ATPase appeared as a distinct entity from Mg-ATPase. Several divalent cations, including Mg2+, inhibited the Ca-ATPase activity. Calmodulin also inhibited, significantly albeit modestly Ca-ATPase. The activity of the enzyme was increased at high pH or in the presence of bicarbonate. The reaction velocity at close-to-physiological concentrations of ATP, Ca2+ and H+ suggests that the consumption of ATP by the Ca-ATPase may account for a major fraction of the overall rate of ATP breakdown in intact islets.

Adenosine Triphosphatases↗
PubMed1995

Activation of adenylate cyclase by divalent cations and polyamines in saponin-treated Dictyostelium discoideum cells.

Binding of an intrinsic agonist (cyclic AMP) to specific receptors on the cell surface induces transmembrane signals for the activation of adenylate cyclase in the cellular slime mold Dictyostelium discoideum. We found that stimulation by CaCl2, MgSO4 or polyamines having two to four positive charges induced the activation of adenylate cyclase in cells treated with saponin. The activation was roughly identical to the stimulation of the intrinsic agonist both in amount and in time course. The intact cells (saponin-untreated cells) responded to neither divalent cations nor polyamines. While saponin is known to have a detergent-like effect and to make the plasma membrane permeable, low molecular weight dyes did not penetrate the plasma membrane under our conditions for the saponin-treatment. Caffeine is known to inhibit the cAMP-induced activation of adenylate cyclase by blocking signal transduction, but not by acting directly on the enzyme [Brenner, M. and Thoms, S.D. (1984) Dev. Biol. 101, 136-146]. We found that caffeine inhibited the cation-induced activation. These results suggest that these divalent and polyvalent cations do not act directly on adenylate cyclase but that they mimic or induce the transmembrane activation signal for adenylate cyclase in the saponin-treated cells.

Adenylyl Cyclases↗
PubMed2001

Low molecular weight milk whey components protect Salmonella senftenberg 775W against heat by a mechanism involving divalent cations.

AIMS: To investigate which components of milk increase the heat resistance of Salmonella senftenberg 775W, and to explore the mechanisms that could be involved in this protective effect. METHODS AND RESULTS: The heat resistance of Salm. senftenberg was determined in a specially designed resistometer in several heating media. The molecules responsible for the thermal protective effect of milk were in the protein fraction, even in the < 3000 Da ultrafiltrate. The protective effect was lost when whey was demineralized. The former protective effect was restored when calcium or magnesium was added. Milk components protected cell envelopes of Salm. senftenberg from heat damage. CONCLUSIONS: The protein fraction and divalent cations were responsible for the protective effect of milk. The whole protective effect on Salm. senftenberg was not the result of the addition of the protective effect of each component, but the result of a synergistic effect of some of them interacting. SIGNIFICANCE AND IMPACT OF THE STUDY: This work could be useful for improving food preservation and hygiene treatments. It also contributes to our knowledge of microbial physiology.

Animals↗
PubMed1987

Inhibition of [3H]kainic acid receptor binding by divalent cations correlates with ion affinity for the calcium channel.

Since the neurotoxicity of kainic acid may be due to the opening of membrane channels for calcium ions for (Ca2+), the effects of Ca2+ and other cations were examined on the specific binding of [3H]kainic acid to membranes from the forebrain of the rat. [3H]Kainic acid bound to a high affinity site (KD = 5.6 nM) that was inhibited in a concentration-dependent manner by Ca2+ ions with an IC50 of 3.2 mM. In the presence of 1 mM Ca2+, the KD of the binding of [3K]kainic acid increased to 11.1 nM without any change in the Bmax. The divalent cations, manganese and cobalt, also were potent inhibitors of the binding of [3H]kainic acid, while barium and strontium were much weaker. The inhibitory effects of Ca2+ on the binding of [3H]kainic acid were blocked by the inorganic Ca2+ channel blockers, cadmium and lanthanum. These data suggest that Ca2+ modulates the binding affinity [3H]kainic acid through an allosteric interaction between the binding site on the Ca2+ channel and the kainic acid receptor.

Animals↗
PubMed1993

Divalent cations, phospholipid asymmetry and osmotic swelling in electrically-induced lysis, cell fusion and giant cell formation with human erythrocytes.

We have previously reported that acidic phospholipids are exposed at the surface of human erythrocytes when the cells are subjected to electrical breakdown. It has now been shown that the prothrombinase assay, which was used previously for the determination of acidic phospholipids, is specific for phosphatidylserine under the conditions of our experiments. In the light of this finding, we have investigated and characterised factors that govern cell lysis, cell fusion, and the formation of giant cells induced by electrical breakdown with human erythrocytes in media of low ionic strength. Divalent cations (1.1 mM) protected the cells against haemolysis, in the order Mn2+ > Ca2+ > Ba2+ > Mg2+ >> Zn2+, whereas about 99% of the cells lysed immediately on breakdown in the presence of Na+ or K+ (2.1 mM), or Al3+ (0.95 mM). The lengths of pearl chains of fused erythrocytes formed was similarly greatest with Mn2+ and decreased progressively with Ba2+, Zn2+, Ca2+ and Mg2+. No cell fusion occurred with Na+, K+, or Al3+. It is suggested that interactions with phosphatidylserine, which is exposed at the cell surface by electrical breakdown, may enable Mn2+, Ba2+ and Ca2+ ions to inhibit cell lysis (via membrane resealing) and facilitate cell fusion. Following electrically-induced cell fusion, erythrocytes round-up into giant cells. It has previously been proposed that Ca2+ ions accelerate the rounding-up process. However, data are presented which show that, as with erythrocytes treated with Sendai virus, the formation of rounded, giant cells following cell fusion depends on the osmotic swelling properties of permeabilised erythrocytes. Osmotic swelling may also have induced any hemi-fused cells present to fuse completely. Zn2+ ions anomalously enabled erythrocytes to round-up very rapidly into giant cells following electrical breakdown. This phenomenon may result from an interaction of Zn2+ ions with cysteine groups in membrane proteins, which decreases the immediate loss of ions that occurs when erythrocytes are subjected to electrical breakdown in low-ionic-strength media.

Cadmium↗
PubMed1983

3h-substance P binding to salivary gland membranes. Regulation by guanyl nucleotides and divalent cations.

With appropriate measures to protect 3H-substance P (3H-SP) from proteolytic degradation and from nonspecific adsorption to glass-fiber filters, we have been able to demonstrate reliably a high-affinity specific binding of 3H-SP to rat submaxillary/sublingual gland membranes with a KD of 1 nM and Bmax of 6 pmoles/g of tissue. The relative potencies of various SP fragments and related analogues in reducing 3H-SP binding parallel their potencies in stimulating phosphatidylinositol turnover, amylase release, and salivation, thus supporting an association of the observed 3H-SP binding site with the physiological SP receptors in this tissue. This binding is selectively stimulated by some divalent cations (Mn2+ greater than Mg2+ greater than Ca2+) but inhibited by several guanyl nucleotides, suggesting a possible linkage to adenylate cyclase. However, no effect of SP on either the basal or the norepinephrine-stimulated adenylate cyclase activity could be demonstrated in salivary gland homogenates.

Adenylyl Cyclases↗
PubMedDate not supplied

Water transport across red-cell membranes following reductive methylation of the major transmembrane protein, Band 3: implications to increased divalent cation membrane permeability.

1H-T-NMR methods in conjunction with normally membrane-impermeable Mn2+ were used to study the effect of reductive methylation of specific lysine residues of Band 3, the major transmembrane protein, on water permeability. At 21 degrees C, the water apparent transverse relaxation time (T2) was decreased by nearly 16% (p less than .00001) for cells with modified Band 3. Atomic absorption measurements of control and methylated cells showed an increased level of Mn2+ in the erythrocyte cytosol following methylation. This increased level of this paramagnetic relaxation agent is sufficient to relax interior water protein to the values obtained. Thus, following specific methylation of band 3, increased membrane permeability to divalent cations is observed. The results are discussed with reference to possible conformation changes of Band 3 following methylation, and the findings are interpreted be mean that the conformation of Band 3 has influence on cation permeability to erythrocyte membranes.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1998

Primase activity of human DNA polymerase alpha-primase. Divalent cations stabilize the enzyme activity of the p48 subunit.

DNA polymerase alpha-primase consists of four subunits, p180, p68, p58, and p48, and comprises two essential enzymatic functions. To study the primase activity of the complex, we expressed cDNAs encoding for the human p58 and p48 subunits either as single proteins or together using Escherichia coli expression vectors. Co-expression of both primase subunits allowed the purification of a heterodimer in high yields that revealed stable primase activity. Purified recombinant p48 subunit showed enzyme activity, whereas purified p58 did not. In contrast to the heterodimer, the primase activity of p48 was unstable. The activity of p48 could be stabilized by the addition of the divalent cations Mg2+ and Mn2+ but not Zn2+. On a poly(dC) template the primase activity was hardly influenced by the monovalent cation potassium. However, by using poly(dT) as a template the recombinant p48 activity was sensitive to salt, whereas recombinant p58-p48 and the bovine DNA polymerase alpha-primase purified from thymus were less sensitive to the addition of monovalent cations. A complex of bacterially expressed primase and baculovirus-expressed p180 and p68 was assembled in vitro and shown to support replication of simian virus 40 DNA in a cell-free system.

Animals↗
PubMed1991

Competitive inhibition of an energy-dependent nickel transport system by divalent cations in Bradyrhizobium japonicum JH.

Both nickel-specific transport and nickel transport by a magnesium transporter have been described previously for a variety of nickel-utilizing bacteria. The derepression of hydrogenase activity in Bradyzhizobium japonicum JH and in a gene-directed mutant of strain JH (in an intracellular Ni metabolism locus), strain JHK7, was inhibited by MgSO4. For both strains, Ni2+ uptake was also markedly inhibited by Mg2+, and the Mg(2+)-mediated inhibition could be overcome by high levels of Ni2+ provided in the assay buffer. The results indicate that both B. japonicum strains transport Ni2+ via a high-affinity magnesium transport system. Dixon plots (1/V versus inhibitor) showed that the divalent cations Co2+, Mn2+, and Zn2+, like Mg2+, were competitive inhibitors of Ni2+ uptake. The KiS for nickel uptake inhibition by Mg2+, Co2+, Mn2+, and Zn2+ were 48, 22, 12, and 8 microM, respectively. Cu2+ strongly inhibited Ni2+ uptake, and molybdate inhibited it slightly. Respiratory inhibitors cyanide and azide, the uncoupler carbonyl cyanide m-chlorophenylhydrazone, the ATPase inhibitor N,N'-dicyclohexylcarbodiimide, and ionophores nigericin and valinomycin significantly inhibited short-term (5 min) Ni2+ uptake, showing that Ni2+ uptake in strain JH is energy dependent. Most of these conclusions are quite different from those reported previously for a different B. japonicum strain belonging to a different serogroup.

Binding, Competitive↗
PubMed1987

Role of magnesium and other divalent cations in ATP-utilizing enzymes.

While free MgATP shows tridentate coordination of Mg2+ by each of the three phosphates, enzyme-bound ATP generally coordinates metals at the beta- and gamma-phosphates and only occasionally at the alpha-phosphate. Enzyme-catalyzed reactions of ATP are in-line nucleophilic displacements at either the alpha-, beta-, or gamma-phosphorus atom, as dictated by the relative positions of the enzyme-bound substrates. The divalent cation activates the attacked phosphoryl group and/or the leaving group of ATP by charge neutralization, electron withdrawal, and by adjustment of the conformation of the polyphosphate chain. Some ATP reactions require an additional divalent cation at the active site to adjust the protein conformation and/or to interact with the other substrate.

Adenosine Triphosphatases↗
PubMed2005

Further application of a two-step heparin affinity chromatography method using divalent cations as eluents: purification and identification of membrane-bound heparin binding proteins from the mitochondrial fraction of HL-60 cells.

Membrane proteins were obtained from the mitochondrial fraction of HL-60 cells by solubilization with octyl glucoside and bound to heparin-gels. Bound proteins were successively eluted with solutions containing increasing concentrations of Mg(2+) in the first and increasing concentrations of Ca(2+) in the second chromatography. After SDS-PAGE and subsequent N-terminal amino acid analysis of proteins on each band, 13 proteins were identified. Fifteen out of the 37 proteins analysed were modified at their N-termini. These results show that this two-step affinity chromatography method using divalent cations as eluents can be applied to a variety of membranes for the isolation of specific proteins.

Amino Acid Sequence↗
PubMed1984

Guanyl nucleotide and divalent cation regulation of cortical S2 serotonin receptors.

Computer-assisted quantitative analysis of radioligand binding to rat cortical S2 serotonin receptors indicates the existence of two affinity states of the same receptor population. Monophasic antagonist competition curves for [3H]ketanserin-labelled sites suggest a uniform population of receptors with one affinity state for antagonists. Biphasic competition curves of agonists suggest that agonists discriminate high- and low-agonist-affinity forms of the S2 receptors. The affinities of agonists for the high- and low-affinity states, and the apparent percentages of high agonist-affinity forms varies with different agonists. The guanine nucleotides GTP and guanyl-5'-imido-diphosphate [Gpp(NH)p], as well as divalent cations, modulate the proportion of the sites with high affinity for agonists as evidenced by their ability to shift the agonist competition curves for [3H]ketanserin-labelled S2 receptors. GTP and Gpp(NH)p effects appear to be agonist-specific, as they do not affect antagonist competition for [3H]ketanserin-labelled S2 receptors, or [3H]ketanserin binding to S2 receptors. ATP and ADP have little or no effect on the binding properties of S2 serotonin receptors, whereas GDP is less potent than GTP. The presence of these specific nucleotide effects are the first evidence suggesting involvement of a guanine nucleotide-binding protein in the mechanism of agonist interaction with the S2 serotonin receptor. In general, the binding properties of [3H]ketanserin-labelled S2 serotonin receptors strongly resemble those of adenylate-cyclase coupled receptors such as the beta-adrenergic, the alpha 2-receptor, and the D-2 dopamine receptor. This may indicate the S2 serotonin receptor is coupled to adenylate cyclase activity, through a GTP binding protein.

Animals↗
PubMed1995

Influence of divalent cations in protein crystallization.

We have tested the effect of several cations in attempts to crystallize the ligand-bound forms of the leucine/isoleucine/valine-binding protein (LIVBP) (M(r) = 36,700) and leucine-specific binding protein (LBP) (M(r) = 37,000), which act as initial periplasmic receptors for the high-affinity osmotic-shock-sensitive active transport system in bacterial cells. Success was achieved with Cd2+ promoting the most dramatic improvement in crystal size, morphology, and diffraction quality. This comes about 15 years after the ligand-free proteins were crystallized. Nine other different divalent cations were tried as additives in the crystallization of LIVBP with polyethylene glycol 8000 as precipitant, and each showed different effects on the crystal quality and morphology. Cd2+ produced large hexagonal prism crystals of LIVBP, whereas a majority of the cations resulted in less desirable needle-shaped crystals. Zn2+ gave crystals that are long rods with hexagonal cross sections, a shape intermediate between the hexagonal prism and needle forms. The concentration of Cd2+ is critical. The best crystals of the LIVBP were obtained in the presence of 1 mM CdCl2, whereas those of LBP, with trigonal prism morphology, were obtained at a much higher concentration of 100 mM. Both crystals diffract to at least 1.7 A resolution using a conventional X-ray source.

Bacterial Proteins↗
PubMed1996

Lateral diffusion in planar lipid bilayers: a fluorescence recovery after photobleaching investigation of its modulation by lipid composition, cholesterol, or alamethicin content and divalent cations.

In spite of the fact that planar lipid bilayers are still the best-suited artificial membrane system for the study of reconstituted ion channels and receptors, data dealing with their physical characterization, especially as regards dynamics, are scanty. A combined electrical and optical chamber was designed and allowed fluorescence recovery after photobleaching recovery curves to be recorded from stable virtually solvent-free bilayers. D, the lateral diffusion coefficient of N-(7-nitrobenzoyl-2-oxa-1,3-diazol-4-yl)-1,2-dihexadecanoyl-sn- glycero-3-phosphoethanolamine, was found to be relatively insensitive to the phospholipid composition (headgroup, chain unsaturation, etc.), whereas inclusion of 33-50% cholesterol in the membrane reduced D by a factor of 2. Divalent cations significantly reduced D of negatively charged bilayers. These results compare well with data gathered on other model and natural systems. In addition, the incorporation of the voltage-dependent pore-former alamethicin did slightly reduce lipid lateral mobility. This study demonstrates the feasibility of such experiments with planar bilayers, which are amenable to physical constraints, and thus offers new opportunities for systematic studies of structure-function relationships in membrane-associating molecules.

Alamethicin↗
PubMed1982

Effect of pH, mono- and divalent cations on the mixing of phosphatidylglycerol with phosphatidylcholine. A monolayer (pi, delta V) and fluorescence study.

The mixing of various molecular species of phosphatidylglycerol and phosphatidylcholine differing in their acyl chain lengths has been studied both in monolayers (pi, delta V), and in water dispersions (fluorescence polarization) with varying pH and ionic strength of the aqueous phase and in the presence of the divalent cations Mg2+ and Ca2+. In dilauroylphosphatidylglycerol/dipalmitoylphosphatidylcholine mixtures, both in monolayers and in water dispersions, no phase separation was detected at pH 2.9 where phosphatidylglycerol was protonated. With dipalmitoylphosphatidylglycerol/dipalmitoylphosphatidylcholine mixtures, in monolayers and at the same pH, no phase separation was detected for surface pressures below pi = 40 mN.m-1. In monolayers, and under ionic conditions such that phosphatidylglycerol was ionized (pH 5.6, 10 mM NaCl) miscibility was observed with dilauroylphosphatidylglycerol and dipalmitoylphosphatidylcholine and also with dipalmitoylphosphatidylglycerol and dilauroylphosphatidylcholine. Varying the ionic strength did not alter the miscibility of these lipids. The divalent cations Mg2+ and Ca2+ did not modify that of dilauroylphosphatidylglycerol with dilauroylphosphatidylcholine or with dipalmitoylphosphatidylcholine. Both in monolayers and in water dispersions, dipalmitoylphosphatidylglycerol and dilauroylphosphatidylcholine appeared to be at least partly miscible, in the presence of magnesium. Only in the presence of calcium and at high surface pressure might the monolayer data account for phase separation between these two lipids. The data presented demonstrate the existence of strong cohesive forces between phosphatidylcholine and phosphatidylglycerol with a marked influence of the former on the physical state of the latter. From an analysis of the delta V data, it is suggested that intrafacial hydrogen bonds may play a significant role in stabilizing phosphatidylcholine/phosphatidylglycerol mixtures.

Calcium↗
PubMed1994

Zinc and other divalent cations inhibit purified leukotriene A4 hydrolase and leukotriene B4 biosynthesis in human polymorphonuclear leukocytes.

Leukotriene A4 hydrolase is a bifunctional metalloenzyme that contains 1 mol of zinc per mole of protein. The primary function of the metal is catalytic and zinc is thus necessary for both its peptidase and its epoxide hydrolase activity. However, at concentrations of zinc exceeding a 1:1 molar ratio (metal:enzyme), we found that zinc acted as an inhibitor with IC50 values of 10 microM for the epoxide hydrolase activity, i.e., the conversion of leukotriene A4 to leukotriene B4, and 0.1 microM for the peptidase activity. The inhibition of both enzyme activities could be reversed by treating the enzyme with chelating agents such as EDTA or dipicolinic acid. Several divalent cations, other than zinc, were also found to inhibit leukotriene A4 hydrolase although with different specificity and potency for the two enzyme activities. Thus, CdSO4 and HgCl2 were effective inhibitors (IC50 approximately 10 microM) of the epoxide hydrolase activity, whereas CoCl2 or MnCl2 were not inhibitory even at concentrations of 1 mM. On the other hand, the peptidase activity was inhibited by CdSO4, NiSO4, HgCl2, MnCl2, CoCl2, and PbNO3, listed in decreasing order of potencies (IC50 0.5-10 microM). In addition, zinc in micromolar concentrations inhibited leukotriene B4 formation in intact human polymorphonuclear leukocytes stimulated by the calcium ionophore A23187 and cell homogenates incubated with arachidonic acid. However, this effect was not related to inhibition of leukotriene A4 hydrolase but rather to a direct or indirect inhibitory effect on the enzyme 5-lipoxygenase in isolated leukocytes. In these cells, 15-lipoxygenase activity was also inhibited by zinc (IC50 5 microM), whereas leukotriene C4 synthase activity in human platelets and rat basophilic leukemia cells was significantly affected only at concentrations > or = 1 mM.

Animals↗