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1.
Dipicolinic acid synthesis inPenicillium citreoviride strain 3114 was inhibited by Ca2+ ions, but not by Ba2+, Cu2+or Fe2+. Among the metals tested, only Zn2+ inhibited the synthesis of dipicolinic acid and promoted sporulation. None of these metals reversed the inhibition by Ca2+ or Zn2+. A mutant 27133-dpa-ca selected for resistance to feedback inhibition by dipicolinic acid: Ca2+ complex showed cross-resistance to inhibition by dipicolinic acid: Zn2+. Both 3114 and271 33-dpa-ca excreted a number of aliphatic and amino acids during secondary metabolism of dipicolinic acid. In the presence of 1000 ppm
of Ca2+, accumulation of citric acid and α-aminoadipic acid was completely inhibited under conditions of inhibition of dipicolinic
acid in parent strain 3114 but not in the mutant. Citric acid with or without Ca2+ did not inhibit thede novo synthesis of dipicolinic acid in the strain 3114. In fact, citric acid in the presence of Ca2+ improved significantly rate of dipicolinic acid synthesis. Apart from resistance to feed back inhibition by dipicolinic acid:
Ca2+ complex, mutant differed from the parent in three other aspectsviz. (i) dipicolinic acid synthesis was not subject to catabolite repression by glucose, (ii) sporulation as well as dipicolinic
acid synthesis was dependent on the presence of Ca2+ ions in the medium and (iii) Mg2+ requirement for the mutant increased three fold. Higher requirement of the Mg2+ could be partially relieved by Ca2+ during secondary metabolism. The results support the inference thatde novo synthesis of dipicolinic acid is regulated through feedback inhibition by dipicolinic acid: Ca2+complex. 相似文献
2.
M. López-Serrano M. A. Ferrer M. A. Pedreño A. Ros Barceló 《Plant Cell, Tissue and Organ Culture》1997,47(3):207-212
Grapevine (Vitis vinifera cv. Monastrell) cell suspension cultures were treated with 1.5 mM fosetyl-Al, a frequently used systemic fungicide for grapevine
diseases caused by oomycetes. These cells showed a reduction in the level of peroxidase activity secreted into the culture
media when compared to non-treated cells, the effect being mainly related to a decrease in the level of the basic B1 peroxidase isozyme. The effect of fosetyl-Al on peroxidase was analogous to that observed with the Ca2+-channel blockers Co2+, Cd2+ and La3+, and was counteracted by Ca2+ ions, but was not reversed when the Ca2+-ionophore A23187 was added to the culture media. Moreover, the effect of fosetyl-Al on peroxidase activity and peroxidase
isozymes was also partially reversed by Mg2+ ions but not by Sr2+, and was accentuated by Ba2+ ions. These results suggested that Ca2+ and Mg2+ ions specifically overcome the inhibitory effect of fosetyl-Al on peroxidase. In this context, an apoplastic Ca2+/Mg2+-displacement hypothesis is proposed for the mechanism of action of fosetyl-Al on peroxidase from grapevine cells. 相似文献
3.
Lyudmila P. Antonyuk Victoria E. Smirnova Alexander A. Kamnev Oksana B. Serebrennikova Maria A. Vanoni Giuliana Zanetti Irina A. Kudelina Oleg I. Sokolov Vladimir V. Ignatov 《Biometals》2001,14(1):13-22
Fully unadenylylated glutamine synthetase (GS) from the endophytic bacterium Azospirillum brasilense Sp245 was isolated and purified. The enzyme was electrophoretically homogeneous and contained strongly bound metal ions, which could not be removed by dialysis. Mn2+, Mg2+, and Co2+ were found to be effective in supporting biosynthetic activity of the A. brasilense GS. Some kinetic properties of Mn2+-activated and Mg2+-activated unadenylylated GS were characterized. Circular dichroism analysis of the enzyme showed that the A. brasilense GS is a highly structured protein: 59% of its residues form -helices and 13% -strands. Removal of the metal ions from the A. brasilense GS by treatment with EDTA resulted in alterations in the enzyme secondary structure. 相似文献
4.
An investigation on the properties of an alkaline protease secreted by Bacillus circulans BM15 strain isolated from a mangrove sediment sample was carried out in order to characterize the enzyme and to test its
potency as a detergent additive. The protease was purified to apparent homogeneity by ammonium sulphate precipitation and
was a 30-kDa protease as shown by SDS-PAGE and its proteolytic activity was detected by casein zymography. It had optimum
activity at pH 7, was stable at alkaline pH range (7 to 11), had optimum temperature of activity 40°C and was stable up to
a temperature of 55°C after incubation for one hour. Hg2+, Zn2+, Co2+, and Cu2+completely inhibited the enzyme activity, while Ca2+, Mg2+, K+ and Fe3+ were enhancing the same. The serine protease inhibitor PMSF and metal chelator EDTA inhibited the activity of this protease
while the classic metalloprotease inhibitor 1, 10 phenanthroline did not show inhibition. The enzyme was stable in SDS, Triton-X-100
and H2 O2 as well as in various commercial detergents after incubation for one hour. The extracellular production of the enzyme, the
pH and temperature stability and stability in presence of oxidants, surfactants and commercial detergents suggest its possible
use as a detergent additive. 相似文献
5.
The effect of ethylenediaminetetraacetate (EDTA) on the mitogen response of porcine lymphocytes and the role of metal ions
in reversal of the inhibitory effect of EDTA were determined. Porcine lymphocyte responses to mitogens were totally suppressed
when serum used to supplement Ca2+, Mg2+-free minimum essential medium (MEM) was dialyzed against saline or saline with 0.2 or 0.60 mM EDTA, but the responses were only partially reduced when the same serum was added to RPMI-1640 medium. The inhibition observed
in MEM could be reversed by adding 1×10−3
M Ca2+ and 1×10−3
M Mg2+ to the dialyzed serum. Serum treated directly with 0.60 mM EDTA completely suppressed blastogenesis in lymphocyte cultures maintained in RPMI-1640 or Ca2+, Mg2+ free MEM. The inhibitory effect of EDTA-treated serum could be completely reversed by adding Zn2+ or a combination of Zn2+ with other cationic ions, or partially reversed by adding Ni2+ or Fe3+. Zn2+ was the most effective ion, in that it was the only ion that, when alone added to the serum, could completely restore lymphocyte
responses to phytohemagglutinin (PHA) or pokeweed mitogen (PWM). 相似文献
6.
A. Sharma C. L. S. N. Rao B. K. Ball S. K. Hasija 《World journal of microbiology & biotechnology》1996,12(6):615-617
Forty bacterial isolates from the effluents of a gelatin factory (Jabalpur, India) were screened for protease activity and the two most potent producers were identified as Bacillus laterosporus and a Flavobacterium sp. The enzymes of both isolates were optimal at pH 8 and 60°C, with maximum activity after 90 min. The enzyme activity of B. laterosporus was suppressed by Fe2+, Mg2+, Mn2+ and Zn2+ ions but was enhanced by Ba2+ and Ca2+. That of Flavobacterium sp. was suppressed by Mg2+ and Mn2+ ions but enhanced by Ba2+, Ca2+ and Fe2+. The enzyme activity of the former was strongly inhibited by KCN, whereas that of the latter was only slightly inhibited by 8-hydroxyquinoline. 相似文献
7.
《Bioscience, biotechnology, and biochemistry》2013,77(11):1859-1862
The effects of some divalent cations on protoplast transfection mediated by polyethylene glycol of Lactobacillus casei ATCC 27092 by PL-1 phage DNA in 50 mM Tris-maleate buffer (pH 6.0) were investigated. The efficiency of transfection increased about 30 times in the presence of 10 mM Ca2+ , Sr2+ increased the transfection rate as well, but Ba2+, Mn2+, and Mg2+ did not. Co2+ and Zn2+ inhibited transfection. The simultaneous use of Ca2+ and Mg2+ increased the transfection efficiency. Impairment of transfection caused by lack of Ca2+ could not be reversed by the addition of Ca2+ later. A decrease in the Ca2+ concentration to an ineffective level before transfection ended immediately inhibited transfection. Protoplasts were transfected with a phage adsorption mutant resistant to PL-1, also, and these metal ions had the same effect. Multiplication of phages in the transfected protoplasts was independent of the presence or absence of calcium ions. Calcium ions seemed to be involved in the entry of PL-1 DNA into the host protoplasts. 相似文献
8.
The toxicity of Cd2+in vivo during the early phases of radish (Raphanus sativus L.) seed germination and the in vitro Cd2+ effect on radish calmodulin (CaM) were studied. Cd2+ was taken up in the embryo axes of radish seeds; the increase in fresh weight of embryo axes after 24 h of incubation was inhibited significantly in the presence of 10 mmol m?3 Cd2+ in the external medium, when the Cd2+ content in the embryo axes was c. 1.1 μmol g?1 FW. The reabsorption of K+, which characterizes germination, was inhibited by Cd2+, suggesting that Cd2+ affected metabolic reactivation. The slight effect of Cd2+ on the transmembrane electric potential of the cortical cells of the embryo axes excluded a generalized toxicity of Cd2+ at the plasma membrane level. After 24 h of incubation, Cd2+ induced no increase in total acid-soluble thiols and Cd2+-binding peptides able to reduce Cd2+ toxicity. Ca2+ added to the incubation medium partially reversed the Cd2+-induced inhibition of the increase in fresh weight of embryo axes and concomitantly reduced Cd2+ uptake. Equilibrium dialysis experiments indicated that Cd2+ bound to CaM and competed with Ca2+ in this binding. Cd2+ inhibited the activation of Ca2+-CaM-dependent calf-brain phosphodiesterase, inhibiting the Ca2+-CaM active complex. Cd2+ reduced the binding of CaM to the Ca2+-CaM binding enzymes present in the soluble fraction of the embryo axes of radish seeds. The possibility that Cd2+ toxicity in radish seed germination is mediated by the action of Cd2+ on Ca2+-CaM is discussed in relation to the in vivo and in vitro effects of Cd2+. 相似文献
9.
Divalent metal ion effects on a mutant histidinol phosphate phosphatase from Salmonella typhimurium 总被引:1,自引:0,他引:1
The effect of divalent metal ions on the activity of a mutant histidinol phosphate phosphatase has been studied. The enzyme was isolated from strain TA387, a mutant of Salmonella typhimurium with a nonsense lesion near the midpoint of the bifunctional hisB gene. Mn2+, Mg2+, Co2+, and Zn2+ shift the optimal pH of phosphatase activity to 6.5 while Be2+ and Ca2+ have no effect on the shape of the pH profile. In the absence of divalent metal ions, the pH optimum is 7.5. Four Me2+ ions, Mn2+, Co2+, Zn2+, and Fe2+ decreased the Km of histidinol phosphate at pH 6.5 from 5.5 mm (without Me2+) to 0.14 mm. Ni2+ and Be2+ increased the Km to 22.2 and 25.0 mm, respectively, and Ca2+ and Mg2+ had an intermediate effect. Changes in maximal velocity were substantially less, only about 2-fold changes being observed. It was shown that the maximal velocity at optimal pH was the same in the absence and presence of Mn2+. Kinetic analysis indicated that there was a rapid equilibrium-ordered addition of Mn2+ to the enzyme before the addition of the substrate, histidinol phosphate. A kimn2+ of 4.3 μm was calculated for the metal ion activation at both pH 6.5 and 7.5. Addition of ethyl-enediaminetetracetate (EDTA) strongly inhibited the phosphatase; inhibition could be reversed by addition of several Me2+ ions, Mg2+ being the most efficient followed by Mn2+. Prolonged incubation with EDTA led to irreversible inactivation. 相似文献
10.
Maria R. Schetinger Angela T. S. Wyse Luis B. Da Silva Claudia K. Barcellos Renato D. Dias Joao J. F. Sarkis 《Biological trace element research》1995,50(3):209-219
Aluminum chloride (AlCl3), a neurotoxic compound, inhibited ATP diphosphohydrolase activity of synaptosomes obtained from cerebral cortex of adult
rats. The metal ion significantly inhibited ATPase and ADPase activities of the enzyme at all concentrations tested in vitro
(0.01, 0.05, 0.5, 5 and 10 mM) in the presence of 1.5 mM calcium. When tested in the absence of Ca2+, and with increasing amounts of Al3+, enzyme activity remained below basal levels, suggesting that the trivalent cation Al3+ is not a substitute for the divalent cation Ca2+ in ATP-Ca2+ and ADP-Ca2+ complexes. The Al3+ inhibition was competitive with respect to Ca2+. The enzyme inhibition was reversed by the addition of deferoxamine (DFO). NaF significantly inhibited ATP diphosphohydrolase
activity, and this inhibition was reversed by the addition of Ca2+ to the medium. Such inhibition was not potentiated by AlF4, which is an inhibitor of cation-transport ATPases. 相似文献
11.
The aminoacylation of tRNA catalysed by valyl-tRNA synthetase (EC 6.1.1.9) and isoleucyl-tRNA synthetase (EC 6.1.1.5) fromMycobacterium smegmatis is dependent on the presence of divalent metal ions. Polyamines alone, in the absence of metal ions, do not bring about aminoacylation.
In the presence of suboptimal concentrations of Mg2+, polyamines significantly stimulate the reaction. Of the cations tested, only Mn2+, Co2+ and Ca2+ can partially substitute for Mg2+ in aminoacylation, and spermine stimulates aminoacylation in the presence of these cations also. At neutral pH, spermine
deacylates nonenzymatically aminoacyl tRNA. AMP and pyrophosphate-dependent enzymatic deacylation of aminoacyl-tRNA (reverse
reaction) is also stimulated by spermine. The inhibitory effect of high concentration of KC1 on aminoacylation is counteracted,
by spermine. The low level of activity between pH 8.5–9.0 at 1.2 mM Mg2+ is restored to normal level on the addition of spermine. The inhibitory effect of high pH on aminoacylation in the presence
of low concentration of Mg2+ is also prevntedvby spemine. 相似文献
12.
Hideyuki Kajiwara Andrew M. Hemmings Hisashi Hirano 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,687(2):726
A tetradecapeptide from ginseng (Panax ginseng) root showing anti-lipolytic activity in an isolated rat fat cell assay was chemically synthesized for analysis of metal binding activities in vitro. Binding activities against several metal ions were analysed by measuring mobility shifts during capillary zone electrophoresis experiments. The ginseng polypeptide (GPP) showed the greatest increase in effective molecular electrophoretic mobility in the presence of Mg2+. Mobility was also affected in the presence of La3+, Mn2+, Ca2+ and Zn2+ ions. Analysis with the dye Stains-all revealed GPP to possess a cation binding site similar to those in Ca2+-binding proteins. GPP thus appears to be a metal binding peptide. The results of this analysis suggested that GPP may perform its anti-lipolytic activities through an ability to modulate the level of free cellular Mg2+ and Mn2+ ions. 相似文献
13.
Ca2+,Mg2+- and Ca2+,Mn2+-dependent and acid DNases were isolated from spermatozoa of the sea urchin Strongylocentrotus intermedius. The enzymes have been purified by successive chromatography on DEAE-cellulose, phenyl-Sepharose, Source 15Q, and by gel filtration, and the principal physicochemical and enzymatic properties of the purified enzymes were determined. Ca2+,Mg2+-dependent DNase (Ca,Mg-DNase) is a nuclear protein with molecular mass of 63 kD as the native form and its activity optimum is at pH 7.5. The enzyme activity in the presence of bivalent metal ions decreases in the series (Ca2+ + Mg2+) > Mn2+ = (Ca2+ + Mn2+) > (Mg2+ + EGTA) > Ca2+. Ca,Mg-DNase retains its maximal activity in sea water and is not inhibited by G-actin and N-ethylmaleimide, whereas Zn2+ inhibits the enzyme. The endogenous Ca,Mg-DNase is responsible for the internucleosomal cleavage of chromosomal DNA of spermatozoa. Ca2+,Mn2+-dependent DNase (Ca,Mn-DNase) has molecular mass of 25 kD as the native form and the activity optimum at pH 8.5. The enzyme activity in the presence of bivalent metal ions decreases in the series (Ca2+ + Mn2+) > (Ca2+ + Mg2+) > Mn2+ > (Mg2+ + EGTA). In seawater the enzyme is inactive. Zinc ions inhibit Ca,Mn-DNase. Acid DNase of spermatozoa (A-DNase) is not a nuclear protein, it has molecular mass of 37 kD as a native form and the activity optimum at pH 5.5, it is not activated by bivalent metal ions, and it is inhibited by N-ethylmaleimide and iodoacetic acid. Mechanisms of the endonuclease cleavage of double-stranded DNA have been established for the three enzymes. The possible involvement of DNases from sea urchin spermatozoa in programmed cell death is discussed. 相似文献
14.
The NADH:ubiquinone oxidoreductase (respiratory complex I) activity of inside-out pig brain submitochondrial particles is
inhibited by endogenous or externally added free fatty acids in time-dependent fashion. The rate and degree of the inhibition
is dramatically increased by Ca2+. The Ca2+-promoted, fatty acid-induced inhibition is pH dependent, this being particularly evident at pH > 8.0. The inhibition is completely
reversed by either EGTA or by bovine serum albumin (BSA). BSA prevents previously described (Kotlyar, A. B., Sled, V. D.,
and Vinogradov, A. D. (1992) Biochim. Biophys. Acta, 1098, 144–150) inhibitory effect of Ca2+ and alkaline pH on the de-active-to-active form transition of complex I. A possible mechanism of synergetic inhibition on
complex I by Ca2+ and fatty acids is discussed. 相似文献
15.
The purpose of the research was to study the purification and partial characterization of thermostable serine alkaline protease
from a newly isolatedBacillus subtilis PE-11. The enzyme was purified in a 2-step procedure involving ammonium sulfate precipitation and Sephadex G-200 gel permeation
chromatography. The enzyme was shown to have a relative low molecular weight of 15 kd by sodium dodecyl sulphate polyacrylamide
gel electrophoresis (SDS-PAGE) and was purified 21-fold with a yield of 7.5%. It was most active at 60°C, pH 10, with casein
as substrate. It was stable between pH 8 and 10. This enzyme was almost 100% stable at 60°C even after 350 minutes of incubation.
It was strongly activated by metal ions such as Ca2+, Mg+2, and Mn+2. Enzyme activity was inhibited strongly by phenylmethyl sulphonyl fluoride (PMSF) and diisopropyl fluorophosphates (DFP)
but was not inhibited by ethylene diamine tetra acetic acid (EDTA), while a slight inhibition was observed with iodoacetate,p-chloromercuric benzoate (pCMB), and β-mercaptoethanol (β-ME). The compatibility of the enzyme was studied with commercial and local detergents in the
presence of 10mM CaCl2 and 1M glycine. The addition of 10mM CaCl2 and 1M glycine, individually and in combination, was found to be very effective in improving the enzyme stability where it
retained 52% activity even after 3 hours. This enzyme improved the cleansing power of various detergents. It removed blood
stains completely when used with detergents in the presence of 10mM CaCl2 and 1M glycine. 相似文献
16.
Kazuki Oka Hiroshi Maeda Shoichi Ikeda 《International journal of biological macromolecules》1983,5(6)
The effects of eight divalent metal ions on fully neutralized poly(S-carboxyethyl-l-cysteine) have been studied by means of circular dichroism. Four ionic species (Cd2+, Cu2+, Zn2+ and Ni2+) effectively induce the β-form, while the other four species (Co2+, Ba2+, Ca2+ and Mg2+) are not effective. Specifically, Mg(ClO4)2 is ineffective, even at 1.86 m. The effect of Cu2+ ions on the polypeptide conformation is significant at pH values other than in the neural range. Comparison of the present results with previous ones from the lower side chain homologue, poly(S-carboxymethyl-l-cysteine), shows that Cd2+ and Zn2+ ions are more effetive but Co2+ ions are much less effective in the polypeptide studied here. Random coils of poly(S-carboxyethyl-l-cysteine) are more soluble while the β-form is less soluble compared with the respective conformations of the lower side-chain homologue. 相似文献
17.
《Journal of receptor and signal transduction research》2013,33(3):220-228
The effect of carvedilol on cytosolic free Ca2+ concentrations ([Ca2+]i) in OC2 human oral cancer cells is unknown. This study examined if carvedilol altered basal [Ca2+]i levels in suspended OC2 cells by using fura-2 as a Ca2+-sensitive fluorescent probe. Carvedilol at concentrations between 10 and 40 µM increased [Ca2+]i in a concentration-dependent fashion. The Ca2+ signal was decreased by 50% by removing extracellular Ca2+. Carvedilol-induced Ca2+ entry was not affected by the store-operated Ca2+ channel blockers nifedipine, econazole, and SK&F96365, but was enhanced by activation or inhibition of protein kinase C. In Ca2+-free medium, incubation with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin did not change carvedilol-induced [Ca2+]i rise; conversely, incubation with carvedilol did not reduce thapsigargin-induced Ca2+ release. Pretreatment with the mitochondrial uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) inhibited carvedilol-induced [Ca2+]i release. Inhibition of phospholipase C with U73122 did not alter carvedilol-induced [Ca2+]i rise. Carvedilol at 5–50 µM induced cell death in a concentration-dependent manner. The death was not reversed when cytosolic Ca2+ was chelated with 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester (BAPTA/AM). Annexin V/propidium iodide staining assay suggests that apoptosis played a role in the death. Collectively, in OC2 cells, carvedilol induced [Ca2+]i rise by causing phospholipase C-independent Ca2+ release from mitochondria and non-endoplasmic reticulum stores, and Ca2+ influx via protein kinase C-regulated channels. Carvedilol (up to 50 μM) induced cell death in a Ca2+-independent manner that involved apoptosis. 相似文献
18.
Effects of Metal Ions on the Conformation and Activity of Acutolysin D from Agkistrodon Acutus Venom
Acutolysin D, isolated from the venom of Agkistrodon acutus, possesses marked haemorrhagic and proteolytic activities. The molecular weight and the absorption coefficients (A
1%
280) of acutolyisn D have been determined to be 47,850 ± 8 amu and 9.3 by mass spectrometer and UV spectrum, respectively. The effects of metal ions on the conformation and activity of acutolysin D have been studied by following fluorescence, circular dichroism and biological activity measurements. Acutolysin D contains two Ca2+-binding sites and two Zn2+-binding sites determined by atomic absorption spectrophotometer. Zn2+ is essential for the enzyme activities of acutolysin D, however, the presence of 1 mM Zn2+ significantly decreases its caseinolytic activity and intrinsic fluorescence intensity at pH 9.0 due to Zn(OH)2 precipitate formation. Ca2+ is important for the structural integrity of acutolysin D, and the presence of 1 mM Ca2+ markedly enhances its caseinolytic activity. Interestingly, the caseinolytic activity which is inhibited partly by Cu2+, Co2+, Mn2+ or Tb3+ and inhibited completely by Cd2+, is enhanced by Mg2+. The fluorescence intensity of the protein decreases in the presence of Cu2+, Co2+, Cd2+ or Mn2+, but neither for Ca2+, Mg2+ nor for Tb3+. Zn2+, Ca2+, Mg2+, Cu2+, Mn2+, Co2+ and Tb3+ have slight effects on its secondary structure contents. In addition, Cd2+ causes a marked increase of antiparallel β-sheet content from 45.5% to 60.2%. 相似文献
19.
Suk-Jin Ha Sang-Yong Kim Jin-Ho Seo Marimuthu Jeya Ye-Wang Zhang Thangadurai Ramu In-Won Kim Jung-Kul Lee 《Bioprocess and biosystems engineering》2009,32(5):697-700
Of various metal ions (Ca2+, Cr3+, Cu2+, Fe2+, Mg2+, Mn2+, Ni2+ and Zn2+) added to the culture medium of Agrobacterium tumefaciens at 1 mM, only Ca2+ increased Coenzyme Q10 (CoQ10) content in cells without the inhibition of cell growth. In a pH-stat fed-batch culture, supplementation with 40 mM of CaCO3 increased the specific CoQ10 content and oxidative stress by 22.4 and 48%, respectively. Also, the effect of Ca2+ on the increase of CoQ10 content was successfully verified in a pilot-scale (300 L) fermentor. In this study, the increased oxidative stress in A. tumefaciens culture by the supplementation of Ca2+ is hypothesized to stimulate the increase of specific CoQ10 content in order to protect the membrane against lipid peroxidation. Our results improve the understanding of Ca2+ effect on CoQ10 biosynthesis in A. tumefaciens and should contribute to better industrial production of CoQ10 by biological processes. 相似文献
20.
Bacillus species producing a thermostable phytase was isolated from soil, boiled rice, and mezu (Korean traditinal koji). The activity of phytase increased markedly at the late stationary phase. An extracellular phytase from Bacillus sp. KHU-10 was purified to homogeneity by acetone precipitation and DEAE-Sepharose and phenyl-Sepharose column chromatographies. Its molecular weight was estimated to be 46 kDa on gel filtration and 44 kDa on SDS-polyacrylamide gel elctrophoresis. Its optimum pH and temperature for phytase activity were pH 6.5-8.5 and 40°C without 10 mM CaCl2 and pH 6.0-9.5 and 60°C with 10 mM CaCl2. About 50% of its original activity remained after incubation at 80°C or 10 min in the presence of 10 mM CaCl2. The enzyme activity was fairly stable from pH 6.5 to 10.0. The enzyme had an isoelectric point of 6.8. As for substrate specificity, it was very specific for sodium phytate and showed no activity on other phosphate esters. The K
m value for sodium phytate was 50 M. Its activity was inhibited by EDTA and metal ions such as Ba2+, Cd2+, Co2+, Cr3+, Cu2+, Hg2+, and Mn2+ ions. 相似文献