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1.
A sample of soluble humic acid from peat-bog water was a glycoconjugate containing 46% of a glycuronoglycan moiety and 54% of a dark-brown chromophore. These accounted for 37% and 63%, respectively, of the titratable acidity of the polymer. Cation-exchange capacities, and cationic selectivity coefficients relative to magnesium ions (KMgMe), were measured on the humic acid for Pb2+, Cu2+, Zn2+, Ba2+, Ca2+, and Sr2+, and compared with those of extractive-free Sphagnum and other mosses, their chlorite holocelluloses, and two soluble fragments of Sphagnum holocellulose, prepared by acidic and alkaline degradation, respectively. The humic acid showed considerably higher KMgMe values than most of the control materials, the enhancement being especially marked for Pb2+, Cu2+, and Ca2+. Scatchard plots showed that both parts of the glycoconjugate contributed to its selectivity, and that the selectivity of the carbohydrate part was greater in the humic acid than in the holocellulose or its soluble fragments. The results are explained by assuming that there are enhanced possibilities for cross-linking in the colloidal humic-acid complexes. 相似文献
2.
Metal Ion Interactions with Phosphoenolpyruvate Carboxylase from Crassula argentea and Zea mays 总被引:1,自引:1,他引:0
Metal ion interactions with phosphoenolpyruvate carboxylase from the CAM plant Crassula argentea and the C4 plant Zea mays were kinetically analyzed. Fe2+ and Cd2+ were found to be active metal cofactors along with the previously known active metals Mg2+, Mn2+, and Co2+. In studies with the Crassula enzyme, Mg2+ yielded the highest Vmax value but also generated the highest values of Km(metal) and Km(pep). For these five active metals lower Km(metal) values tended to be associated with lower Km(pep) values. PEP saturation curves showed more kinetic cooperativity than the corresponding metal saturation curves. The activating metal ions all have ionic radii in the range of 0.86 to 1.09 Å. Ca2+, Sr2+, Ba2+, and Ni2+ inhibited competitively with respect to Mg2+, whereas Be2+, Cu2+, Zn2+, and Pd2+ showed mixed-type inhibition. Vmax trends with the five active metals were similar for the C. argentea and Z. mays enzymes except that Cd2+ was less effective with the maize enzyme. Km(metal) values were 10- to 60-fold higher in the enzyme from Z. mays. 相似文献
3.
Standard free energy maps for the hydrolysis of ATP as a function of pH and metal ion concentration: comparison of metal ions 总被引:1,自引:0,他引:1
The observed equilibrium constant Kobs for the hydrolysis of ATP to ADP and inorganic phosphate has been calculated as a function of pH and metal ion concentration pM (- log [M]) at 25 °C and μ = 0.2 with the use of literature values of the acid dissociation and complex dissociation constants for the phosphates.The resulting standard free energy changes ΔG °′ are presented by means of contour diagrams for the range pH 4–10 and pM 1–7. These maps summarize the results of some 1900 calculations per diagram, and clearly simulate a differential effect of the metal ions of interest, including Mg2+, Ca2+, Sr2+, Mn2+, Li+, Na+ and K+, on the equilibrium hydrolysis of ATP. 相似文献
4.
H. Jachmann R.C.V.J. Zweypfenning J.N. Van der Molen 《Journal of insect physiology》1982,28(11):943-946
Ionic composition of the haemolymph and electrophysiological responses of tarsal taste hairs were determined for individual flies of the species Calliphora vicina, in order to test the hypothesis that electrophysiological response values of individual flies are correlated with the ionic composition. Instead of flame photometry we used isotachophoresis to determine the ionic composition; only non-bound ions contribute to the result. Because of this we found lower concentration values than those reported so far. There was a strong correlation between the concentrations of the cations Na+, K+ and Mg2+, while Ca2+ was not related with any other cation. A significant correlation was shown to exist between the response of taste cells and the Na+, K+ and Ca2+ content in the haemolymph. These correlations explain, at least partly, the systematic differences in taste cell responses between flies, as reflected in interindividual variability. 相似文献
5.
The capacity of various metal ions to support activation of bovine factor IX, by the coagulant protein of Russell's Viper venom, has been examined. The following metal ions, at concentrations which saturate their effect, promoted activation of factor IX, at approximately equal efficiency: Ca2+, Mn2+, Sr2+, and Co2+, Other metal ions, i.e., Ba2+, and Mg2+, at saturating concentrations, led to a maximum rate of activation of factor IX of 25%, compared to Ca2+, The lanthanides, Gd2+, and Tb3+, also promoted activation in this system, at maximal rates of approximately 15%, compared to Ca2+, In this study, it was also discovered that the esterase activity of bovine factor IXa was dependent upon the presence of metal ions. Utilizing α-N-benzoyl-l-arginine ethyl ester as the substrate, steady state kinetic analysis in the absence of metal ion indicated that the Km and Vmax for this substrate was 20 mm and 2.9 μmol substrate cleaved min?1 mg?1 of factor IXa, respectively, at pH 8.0 and 30 °C. In the presence of optimal concentrations of Ca2+, Mn2+, Mg2+, Sr2+, and Ba2+, the Vmax values for this same substrate increased to 6.7, 5.9, 5.0, 5.0, and 3.7 μmol cleaved min?1 mg?1 of factor IXa, respectively. None of these metal ions had an affect on the Km value of this substrate. 相似文献
6.
7.
Magnesium-dependent adenosine triphosphatase has been purified from sheep kidney medulla plasma membranes. The purification, which is based on treatment of a kidney plasma membrane fraction with 0.5% digitonin in 3 mm MgCl2, effectively separates the Mg2+-ATPase from (Na+ + K+)-ATPase present in the same tissue and yields the Mg2+-ATPase in soluble form. The purified enzyme is activated by a variety of divalent cations and trivalent cations, including Mg2+, Mn2+, Ca2+, Co2+, Fe2+, Zn2+, Eu3+, Gd3+, and VO2+. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme shows two bands with Rf values corresponding to molecular weights of 150,000 and 77,000. The larger peptide is phosphorylated by [γ-32P]ATP, suggesting that this peptide may contain the active site of the Mg2+-ATPase. The Mg2+-ATPase activity is unaffected by the specific (Na+ + K+)-ATPase inhibitor ouabain. 相似文献
8.
Precipitation of Metallic Cations by the Acidic Exopolysaccharides from Bradyrhizobium japonicum and Bradyrhizobium (Chamaecytisus) Strain BGA-1
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J. Corzo M. Len-Barrios V. Hernando-Rico A. M. Gutierrez-Navarro 《Applied microbiology》1994,60(12):4531-4536
The interaction between the acidic exopolysaccharides produced by two Bradyrhizobium strains and several metal cations has been studied. Aqueous solutions in the millimolar range of Fe3+ but not of Fe2+ precipitated the exopolysaccharides from Bradyrhizobium (Chamaecytisus) strain BGA-1 and, to a lesser extent, Bradyrhizobium japonicum USDA 110. The precipitation was pH dependent, with a maximum around pH 3. The precipitate was redissolved by changing the pH and by Fe3+ reduction or chelation. Deacetylation of B. japonicum polysaccharide increased its precipitation by Fe3+. At pH near neutrality, the polysaccharide from Bradyrhizobium (Chamaecytisus) strain BGA-1 stabilized Fe3+ solutions, despite the insolubility of Fe(OH)3. Aluminum precipitated Bradyrhizobium (Chamaecytisus) polysaccharide but not the polysaccharide produced by B. japonicum. The precipitation showed a maximum at about pH 4.8, and the precipitate was redissolved after Al3+ chelation with EDTA. Precipitation was inhibited by increases in the ionic strength over 10 mM. Bradyrhizobium (Chamaecytisus) polysaccharide was also precipitated by Th4+, Sn2+, Mn2+, and Co2+. The presence of Fe3+ increased the exopolysaccharide precipitation by aluminum. No precipitation, gelation, or increase in turbidity of polysaccharide solutions occurred when K+, Na+, Ca2+, Mg2+, Cu2+, Cd2+, Pb2+, Zn2+, Hg2+, or U6+ was added at several pH values. The results suggest that the precipitation is based on the interaction between carboxylate groups from different polysaccharide chains and the partially hydrolyzed aquoions of Fe3+, Al3+, Th4+, and Sn2+. 相似文献
9.
A novel copper, zinc superoxide dismutase (CuZnSOD) was purified to homogeneity from the liver of an animal well adapted to the stressful living conditions of the desert, the camel (Camelus dromedarius). The biochemical properties of camel liver CuZnSOD were examined. The purified enzyme had a native molecular weight of 28 kDa, as judged by gel filtration chromatography, and showed a single band at 27 kDa on SDS-PAGE, indicating that it is a monomeric protein. Optimal activity of the purified enzyme occurred at 43 °C and pH 6.0, and the activation energy was 1.42 kJ/mol. CuZnSOD activity was strongly inhibited by β-ME, DTT, H2O2 and SDS and slightly inhibited by EDTA, NaN3 and PMSF. Al3+, Ca2+, Cd2+, Mg2+ and Zn2+ stimulated CuZnSOD activity, whereas Ba2+, Co2+, Fe2+ and Ni2+ inhibited it. The purified enzyme contained 0.010 µg of Cu and 0.69 µg of Zn per mg of protein. Km, Vmax, kcat and kcat/Km values for NBT and riboflavin were 16.27 and 0.16 µM, 20.85 and 21.54 U/mg, 9.65 and 9.97 s−1, and 0.59 and 62.33 s-1 µM−1, respectively. Camel liver CuZnSOD exhibited unique biochemical properties compared to those of other CuZnSODs, including lower molecular weight with a monomeric structure, higher optimum temperature, very low Ea, very low optimum pH, very low contents of Cu and Zn, and higher affinity, turnover number and catalytic efficiency for riboflavin. These unique properties of camel liver CuZnSOD might be related to the ability of this animal to inhabit stressful desert conditions. 相似文献
10.
Hua Liu Xinxin Zhang Tetsuo Takano 《Biochemical and biophysical research communications》2009,383(4):392-3870
The gene for a novel cation/H+ antiporter from Puccinellia tenuiflora, PutCAX1, was cloned from a cDNA library. The PutCAX protein was localized in the vacuolar membrane using a GFP marker. Several yeast transformants were created using full-length and truncated form of PutCAX1 and their growths in the presence of various cations (Mg2+, Ca2+, Mn2+, Ni2+, Cu2+, Zn2+, Se2+, and Ba2+) were analyzed. PutCAX1 expression was found to affect the response to Ca2+ and Ba2+ in yeast. The PutCAX1 and C-terminally truncated PutCAX1 (ΔCPutCAX1) transformants grew in the presence of 70 mM Ca2+ as well as in the presence of 8 mM Ba2+. However, the ΔCPutCAX1 transformant was able to grow in the presence of 20 mM Ba2+ while the PutCAX1 transformant could not. On the other hand, expression of the N-terminally truncated form and the N- and C-terminally truncated form failed to suppress the Ca2+ or Ba2+ sensitivity of yeast. These results suggest that PutCAX1 can complement the active Ca2+ transporters at some level and confer yeast Ba2+ tolerance, and that the N- and C-terminal regions of PutCAX1 play important roles in increasing the Ca2+ or Ba2+ tolerance of yeast. 相似文献
11.
The absorption characteristics of Cd2+ by 10- to 12-day-old soybean plants (Glycine max cv Williams) were investigated with respect to influence of Cd concentration on adsorption to root surfaces, root absorption, transport kinetics and interaction with the nutrient cations Cu2+, Fe2+, Mn2+, and Zn2+. The fraction of nonexchangeable Cd bound to roots remained relatively constant at 20 to 25% of the absorbed fraction at solution concentration of 0.0025 to 0.5 micromolar, and increased to 45% at solution concentration in excess of 0.5 micromolar. The exchangeable fraction represented 1.4 to 32% of the absorbed fraction, and was concentration dependent. Using dinitrophenol as a metabolic inhibitor, the `metabolically absorbed' fraction was shown to represent 75 to 80% of the absorbed fraction at concentration less than 0.5 micromolar, and decreased to 55% at 5 micromolar. At comparatively low Cd concentrations, 0.0025 to micromolar 0.3, root absorption exhibited two isotherms with K2 values of 0.08 and 1.2 micromolar. Root absorption and transfer from root to shoot of Cd2+ was inhibited by Cu2+, Fe2+, Mn2+, and Zn2+. Analyses of kinetic interaction of these nutrient cations with Cd2+ indicated that Cu2+, Fe2+, Zn2+, and possibly Mn2+ inhibited Cd absorption competitively suggesting an involvement of a common transport site or process. 相似文献
12.
Aluminum is a major constituent of most soils and limits crop productivity in many regions. Amelioration is of theoretical as well as practical interest because understanding amelioration may contribute to an understanding of the mechanisms of toxicity. In the experiments reported here 2-day-old wheat (Triticum aestivum L. cv Tyler) seedlings with 15-millimeter roots were transferred to solutions containing 0.4 millimolar CaCl2 at pH 4.3 variously supplemented with AlCl3 and additional amounts of a chloride salt. Root lengths, measured after 2 days in the test solutions, were a function of both Al activity and the cation activity of the added salt. Percent inhibition = 100 {Al3+}/({Al3+} + Km + α{C}β) where {Al3+} is the activity of Al3+ expressed in micromolar, {C} is the activity of the added cation expressed in millimolar, and Km (= 1.2 micromolar) is the {Al3+} required for 50% inhibition in the absence of added salt. For Ca2+, Mg2+, and Na+ the values of α were 2.4, 1.6, and 0.011, respectively, and the values for β were 1.5, 1.5, and 1.8, respectively. With regard to relative ameliorative effectiveness, Ca2+ > Mg2+ ≈ Sr2+ K+ ≈ Na+. Other cations were tested, but La3+, Sc3+, Li+, Rb+, and Cs+ were toxic at potentially ameliorative levels. The salt amelioration is not solely attributable to reductions in {Al3+} caused by increases in ionic strength. Competition between the cation and Al for external binding sites may account for most of the amelioration. 相似文献
13.
Tadashi Aogaichi Janine Evans Jerome Gabriel Gerhard W.E. Plaut 《Archives of biochemistry and biophysics》1980,204(1):350-360
(i) The activity of purified NAD-specific isocitrate dehydrogenase from bovine heart was stimulated by free Ca2+ in the presence of ADP and subsaturating levels of magnesium isocitrate, but not in absence of ADP. However, Ca2+ was not absolutely required for ADP activation. This was particularly apparent when free Mg2+ was kept low (0.0024–0.020 mm) and the substrate magnesium dl-isocitrate ranged from 0.07–0.25 mm. When kinetic constants were determined at pH 7.4 under these conditions and in the absence of ethylene glycol bis(β-aminoethyl ether) N,N′-tetraacetate, Ca2+ had little or no effect on Km (app) for ADP; the stimulation of rate by Ca2+ was mainly due to increased V (app). With subsaturating ADP, there was an interdependence in the interaction of the enzyme with substrate and Ca2+. Thus, with ADP constant (0.30 mm) the values of Km (app) for magnesium dl-isocitrate declined from 0.35 mm at zero Ca2+ to 0.19 mm with saturating Ca2+ without affecting V; Km (app) for free Ca2+ declined with increasing magnesium isocitrate to a limiting Km of 0.3 μm. (ii) Ethylene glycol bis(β-aminoethyl ether)-N,N′-tetraacetate, frequently used as a calcium buffer, inhibited enzyme activity with and without ADP. (iii) The enzyme was not inhibited by the calmodulin inhibitors trifluoperazine and chlorpromazine. Inhibition by lanthanide ions of the isocitrate dehydrogenase was competitive with magnesium isocitrate and not with respect to Ca2+. The values of Kis (1.8 to 3.1 μm) for La3+, Yb3+, Gd3+, Eu3+, Tb3+, and Er3+ were about two orders of magnitude smaller than Km for magnesium dl-isocitrate. 相似文献
14.
Nèjia Farhat Mokded Rabhi Marianna Krol Zouhaier Barhoumi Alexander G. Ivanov Avery McCarthy Chedly Abdelly Abderrazak Smaoui Norman P. A. Hüner 《Acta Physiologiae Plantarum》2014,36(8):2157-2165
In the present work, magnesium deficiency effects were studied in Sulla carnosa plants grown in nutrient solution containing 1.50, 0.05, 0.01, and 0.00 mM Mg2+. After 5 weeks of treatment, fully expanded leaves were harvested to study their morphological and ultrastructural changes, as well as their carbohydrate, pigment, and Mg2+ concentrations. In control plants, leaves were well developed with remarkable green color. Down to 0.05 mM Mg2+, no chlorosis symptom was recorded, but below this concentration, mature leaves showed an appearance of interveinal chlorosis that was much more pronounced at 0.00 mM Mg2+ with the development of necrotic spots. Optima of chlorophyll a, chlorophyll b, and carotenoid concentrations were observed at 0.05 and 1.50 mM Mg2+; leaf magnesium concentration was severely reduced at 0.05 mM Mg2+. A significant decrease in pigment concentrations was noticed at 0.01 mM Mg2+, but the lowest values were recorded at 0.00 mM Mg2+. Enzymatic assays showed an increase in the accumulation of soluble sugars and starch with decreasing Mg2+ concentration. These results were in accordance with those of ultrastructural studies that revealed a marked alteration of chloroplasts in leaves of deficient plants. These chloroplasts were round and bigger as a result of a massive accumulation of oversized starch grains with disrupted thylakoids. As a whole, 1.50, 0.05, and 0.01 mM Mg2+ were found optimal, suboptimal, and deficient concentrations, respectively, the latter showing no significant difference with absolute Mg2+ absence (0.00 mM Mg2+). 相似文献
15.
《The International journal of biochemistry》1986,18(4):345-350
- 1.1. [3H]diazepam ([3H]DZ) was used as a ligand to study the effects of Ca2+ on benzodiazepine binding to rat brain membranes.
- 2.2. [3H]DZ bound at a single class of binding sites showing KD and Bmax values of 5.4 nM and 852 fmol/mg protein respectively. These values are consistent with previous reports.
- 3.3. Amongst the various divalent cations tested Mg2+, Fe2+, Cd2+, and Sr2+ had no significant effect on [3H]DZ binding. Mn2+, Ba2+, Co2+, Ni2+ and La2+ enhanced radioligand binding, whereas Ca2+, Zn2+ and Pb2+ inhibited [3H]DZ binding to brain freeze-thawed membranes.
- 4.4. The inhibition of [3H]DZ binding by Ca2+ was concentration-dependent. 50% inhibition occurred at a Ca2+ concentration of 5.6mM. The Hill coefficient for the inhibition was 1.03, displaying noncoperativity. The effect of Ca2+ on [3H]DZ binding could be prevented by La3+ but was not reversed by EGTA.
- 5.5. A kinetic analysis of Ca2+ inhibition of [3H]DZ binding indicates that Ca2+ inhibited competitively. Analysis of binding isotherms indicates that both KD and Bmax were altered at the [3H]DZ binding sites. The marked increase in KD value in the presence of Ca2+ (5 mM) can be explained by a drastic increase in the dissociation rate constant.
- 6.6. It was suggested that Ca2+ may induce a conformational change in the diazepam binding sites on rat brain membranes. The unchanged Hill coefficient in the presence or absence of Ca2+ indicates that a single population of binding sites was labeled by [3H]DZ.
- 7.7. The calmodulin antagonists, trifluoperazine and W-7 were weak inhibitors of [3h]dz binding.
16.
Influence of calcium and magnesium on ethylene production by apple tissue slices 总被引:4,自引:3,他引:4
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The decline in ethylene production in apple (Pyrus malus L. cv. Golden Delicious) tissue slices during 24 hours incubation in 600 millimolar sorbitol and 10 millimolar 2-(N-morpholino)ethanesulfonic acid buffer (pH 6.0) is recognized as a senescent phenomenon. The inclusion of very high concentrations (100 millimolar) of Ca2+, Mg2+, or Ca2+ plus Mg2+ severely inhibited ethylene production during the first 6 hours of incubation. However, after 6 hours and up to 24 hours the ethylene-forming system was stablized. These high concentrations of Ca2+, Mg2+, or Ca2+ plus Mg2+ virtually eliminated lipid peroxidation and protein leakage from these slices. Also conversion of 1-aminocyclopropane-1-carboxylic-1-acid to ethylene and the influence of indoleacetic acid on ethylene production was stabilized after 24 hours of incubation by these high concentrations of Ca2+, Mg2+, and Ca2+ plus Mg2+. Addition of divalent ionophores severely inhibited ethylene production, but this inhibition was prevented by Ca2+ in concentrations greater than the ionophore. These data suggest that the loss of ethylene production by aging tissue slices results from degradation of membranes. They support previous work that indicates that the ethylene-forming system, perhaps the segment of the pathway from 1-aminocyclo-propane-1-carboxylic-1-acid to ethylene, resides in the plasma membrane. 相似文献
17.
Junxin Zhao Maomao Ma Zheling Zeng Ping Yu Deming Gong Shuguang Deng 《Journal of enzyme inhibition and medicinal chemistry》2021,36(1):248
A novel lipase, SCNL, was isolated from Staphylococcus caprae NCU S6 strain in the study. The lipase was purified to homogeneity with a yield of 6.13% and specific activity of 502.76 U/mg, and its molecular weight was determined to be approximately 87 kDa. SCNL maintained above 80% of its initial activity at a wide range of temperatures (20–50 °C) and pH values (6–11), with an optimal temperature at 40 °C and optimal pH at 9.0 with p-nitrophenyl palmitate as a substrate. SCNL exhibited a higher residual activity than the other staphylococcal lipases in the presence of common enzyme inhibitors and commercial detergents. The lipase activity was enhanced by organic solvents (isooctane, glycerol, DMSO and methanol) and metal ions (Na+, Ba2+, Ca2+, and Mn2+). The Km and Vmax values of SCNL were 0.695 mM and 262.66 s−1 mM−1, respectively. The enzyme showed a preference for p-NP stearate, tributyrin and canola oil. These biochemical features of SCNL suggested that it may be an excellent novel lipase candidate for industrial and biotechnological applications. 相似文献
18.
Properties of partially purified NADP-malic enzyme (EC 1.1.1.40) from glumes of developing wheat grains were examined. The pH optimum for enzyme activity was influenced by malate and shifted from 7.3 to 7.6 when the concentration of malate was increased from 2 to 10 mM. The Km values, at pH 7.3, for various substrates were: malate, 0.76 mM; NADP, 20 μM and Mn2+, 0.06 mM. The requirement of Mn2+ cation for enzyme activity could be partially replaced by Mg2+ or Co2+. Mn2+ dependent enzyme activity was inhibited by Pb2+, Ni2+, Hg2+, Zn2+, Cd2+, Al3+ and Fe3+. During the reaction, substrate molecules (malate and NADP) reacted with enzyme sequentially. Activity of malic enzyme was inhibited by products of the reaction viz pyruvate, HCO3? and NADPH2. At a limiting fixed concentration of NADP, these products induced a positive cooperative response to increasing concentrations of malate. 相似文献
19.
In this paper, we investigated the properties of trehalose-6- phosphate synthase (SfTps1) inSaccharomycopsis fibuligera sdu a high-trehalose-accumulating strain. The purified SfTps1 showed a band on Native-PAGE and SDS-PAGE of about 66 kDa. The optimal pH and temperature of the purified enzyme were 6.6 and 37 °C, respectively. The enzyme was activated by Ca2+, K+ and Mg2+, inhibited by Mn2+, Cu2+, Fe3+, Hg2+ and Co2+. Iodoacetic acid, EDTA and PMSF had inhibitory effect on the enzyme activity. Km values of the enzyme for glucose-6-phosphate and UDP-glucose were 38.6 mM and 9.3 mM, respectively. The effects of various stress conditions on SfTps1 activity and trehalose content in this strain were also studied. Neither the activation of SfTps1 nor the change in trehalose content was observed under stress exposure ofSaccharomycopsis fibuligera cells. Our results indicate that the SfTps1 protein and trehalose metabolism in response to stress conditions inSaccharomycopsis fibuligera clearly differ from that ofSaccharomyces cerevisiae and most of other eukaryotes. 相似文献
20.
《Process Biochemistry》2014,49(12):2114-2121
The codon-optimized carbonic anhydrase gene of Persephonella marina EX-H1 (PMCA) was expressed and characterized. The gene with the signal peptide removed, PMCA(sp−), resulted in the production of approximately five times more purified protein than from the intact gene PMCA using an Escherichia coli expression system. PMCA(sp−) is formed as homo-dimer complex. PMCA(sp−) has a wide pH tolerance (optimum pH 7.5) and a high thermostability even at 100 °C (88 min of thermal deactivation half-life). The melting temperature for PMCA(sp−) was 84.5 °C. The apparent kcat and Km values for CO2 hydration were 3.2 × 105 s−1 and 10.8 mM. The activity of the PMCA(sp−) enzyme was enhanced by Zn2+, Co2+, and Mg2+, but was strongly inhibited by Cu2+, Fe3+, Al3+, Pb2+, Ag+, and Hg2+. PMCA(sp−) readily catalyzed the hydration of CO2, precipitating CaCO3 as calcite in the presence of Ca2+. 相似文献