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1.
A new low-molecular-weight peptide with phenol oxidase activity, named Pc factor, was isolated and purified from liquid culture of a white-rot basidiomycete Phanerochaete chrysosporium. Its molecular weight was about 600 Da estimated by gel-filtration. Three amino acids Glu, Gly and Val were detected in hydrolysate. Absorption peaks corresponding to amino acids and peptide were observed by UV and IR spectra analysis. And the signal of Cα of amino acid was also detected by 13C-NMR method. Pc factor had high thermostability and remained active in weakly alkalescent pH range. It could chelate Fe3+ and reduce it to Fe2+, but no hydroxyl radical HO9642; could be detected during the reaction process. It could oxidize phenolic lignin-model compounds such as 2,6-dimethoxyphenol (2,6-DMP), 2,2¢-azinobis (3-ethylbenzathiazoline-6-sulfinic acid) (ABTS) and syringaldazine in the absence of Mn2+ and H2O2. These characteristics differed greatly from those of manganese peroxi-dases. The oxidative catalysis of Pc factor can be enhanced by certain metal ions such as Cu2+ and Mn2+ etc., and O2 molecule was necessary for this reaction. In summary, Pc factor may function as an electron carrier in this novel oxidation-reduction system. 相似文献
2.
A peptide-mediated and hydroxyl radical HO*-involved oxidative degradation of cellulose by brown-rot fungi 总被引:6,自引:0,他引:6
A special low-molecular-weight peptide named Gt factor, was isolated and purified from the extracellular culture of brown-rot fungi Gloeophyllum trabeum via gel filtration chromatography and HPLC. It has been shown to reduce Fe3+ to Fe2+. Electron paramagnetic resonance (EPR) spectroscopy revealed Gt factor was able to drive H2O2 generation via a superoxide anion O2
.- intermediate and mediate the formation of hydroxyl radical HO. in the presence of O2. All the results indicated that Gt factor could oxidize the cellulose, disrupt the inter- and intrahydrogen bonds in cellulose chains by a HO. -involved mechanism. This resulted in depolymerization of the cellulose, which made it accessible for further enzymatic hydrolysis. 相似文献
3.
Richard H. Stadler Jovanka Markovic Robert J. Turesky 《Biological trace element research》1995,47(1-3):299-305
The anti- and pro-oxidative effects of phenolic compounds and antioxidants were studied in two different in vitro model systems
utilizing ethyl linoleate and 2′-deoxyguanosine (2′-dG) as oxidative substrates, and a Fenton reaction (H2O2, Fe2+) to initiate oxidation. Oxidation of the biomolecules in both model systems exhibited dose dependency. In the 2′-dG assay,
oxidation was closely related to H2O2 generation, which occurred during autoxidation of the phenolics. Hydroxylating activity was greatly enhanced by Mn2+ and Cu2+, but not by Zn2+ or Co2+. Ethyl linoleate peroxidation was inhibited by low concentrations of catechol, quercitin, and instant coffee. However, peroxidation
was promoted by high concentrations of the same compounds, probably by recycling of chelated inactive Fe3+ to the active Fe2+ state. 相似文献
4.
Human β-mannosidase (MANB) was purified to homogeneity directly from lysosomes by using mannosamine conjugated magnetic (Fe3O4) nanoparticles, DE-52 cellulose, and sephadex G-200 chromatography. Fe3O4 nanoparticles were synthesized and utilized ammonia to attach the amino group on the nanoparticles. The particles were covalently
attached with D-mannosamine by cross linker glutaraldehyde and confirmed by FTIR spectroscopy. In FTIR analysis, the peaks
appeared at 2,356.6 cm−1 for −N = CH linkage and at 3,378.4 cm−1, 3,664.9 cm−1 for −OH groups confirmed the conjugation of D-mannosamine with Fe3O4 nanoparticles. Results showed a single band of 97 kDa of purified MANB in SDS-PAGE. The isoelectric point was 4.5 and the
Km and Vmax values were 2.51 mM and 0.315 μM/min/mg, respectively. The purification fold was 329 with 68% yield. The optimal activity
was at pH 5.0 and 75% activity was stable in 20% glycerol at 4°C. The enzyme activity was inhibited by Ni2+, Zn2+, Cd2+, Cu2+, Mo2+, Ag+1, iodoacetate, SDS, DMF, DMSO, ethanol, and acetone; slightly reduced by Pb2+, Co2+, EDTA, DTT, and β-mercaptoethanol. The activity was not affected by Mg2+, Mn2+, Sn2+, Ca2+, Fe3+, PMSF, Triton X-100, D-mannosamine, D-mannose, D-mannitol, D-glucose, and D-fructose. The homogeneity of MANB enzyme was
further confirmed by 2D-PAGE and immunoblot. This is the first novel report of conjugation of D-mannosamine with Fe3O4 nanoparticles for purification of human MANB enzyme. 相似文献
5.
6.
Sediment pore water concentrations of Fe2+, Mn2+, NH
inf4
sup+
and CH4 were analyzed from both diver-collected cores and anin situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station
with a hemispheric chamber (including DO probe and recorder) subtending a known area of sediments. The average SOD was 9.4
mM m−2 day−1 (0.3 g m−2 day−1). From pore water gradients within the near-surface zone, the chemical flux across the interface was calculated indirectly
using Fick's first law modified for sediments. These calculations, using core and peeper gradients, always showed sediment
loss to overlying waters, and variations between the two techniques differed by less than an order of magnitude for Fe2+ and CH4. The transport of these reduced constituents can represent a sizeable oxygen demand, ranging from less than 1% for Fe2+ and Mn2+ to as high as 26% for NH
inf4
sup+
, and 30% for CH4. The average flux of these constituents could account for about a third of the SOD at the sediment-water interface of this
station. 相似文献
7.
Chang-Jun Ji Jung-Hoon Kim Young-Bin Won Yeh-Eun Lee Tae-Woo Choi Shin-Yeong Ju Hwan Youn John D. Helmann Jin-Won Lee 《The Journal of biological chemistry》2015,290(33):20374-20386
In many Gram-positive bacteria PerR is a major peroxide sensor whose repressor activity is dependent on a bound metal cofactor. The prototype for PerR sensors, the Bacillus subtilis PerRBS protein, represses target genes when bound to either Mn2+ or Fe2+ as corepressor, but only the Fe2+-bound form responds to H2O2. The orthologous protein in the human pathogen Staphylococcus aureus, PerRSA, plays important roles in H2O2 resistance and virulence. However, PerRSA is reported to only respond to Mn2+ as corepressor, which suggests that it might rely on a distinct, iron-independent mechanism for H2O2 sensing. Here we demonstrate that PerRSA uses either Fe2+ or Mn2+ as corepressor, and that, like PerRBS, the Fe2+-bound form of PerRSA senses physiological levels of H2O2 by iron-mediated histidine oxidation. Moreover, we show that PerRSA is poised to sense very low levels of endogenous H2O2, which normally cannot be sensed by B. subtilis PerRBS. This hypersensitivity of PerRSA accounts for the apparent lack of Fe2+-dependent repressor activity and consequent Mn2+-specific repressor activity under aerobic conditions. We also provide evidence that the activity of PerRSA is directly correlated with virulence, whereas it is inversely correlated with H2O2 resistance, suggesting that PerRSA may be an attractive target for the control of S. aureus pathogenesis. 相似文献
8.
The oxidation of Mn2+-pyrophosphate to Mn3+ by superoxide (O2?) was quantitative as evidenced from the formation of Mn3+-pyrophosphate and hydrogen peroxide and from the inhibition by superoxide dismutase. Using the competitive relation between Mn2+-pyrophosphate and superoxide dismutase for the O2?, the rate constant of Mn2+ oxidation was estimated to be about 6 × 106m?1 s?1. The oxidation of Mn2+-pyrophosphate by illuminated chloroplasts was also indicated to be stoichiometrically induced by O2?. In the presence of saturating amounts of the Mn2+, a double enhancement of hydrogen peroxide production and triple uptake of oxygen were found, as expected from the oxidation of Mn2+-pyrophosphate by O2?. Anaerobiosis or superoxide dismutase annuled these increments. We propose that the O2? generated as the sole initial step of the Mehler reaction oxidized Mn2+-pyrophosphate, and we discuss the role of free manganese in chloroplasts. 相似文献
9.
Addition of microgram quantities (5–10 μg per 2 ml) of Mn2+, Fe2+, and Mo2+ increases the intensity of color developed by amino acids two- to three-fold when reacting with ninhydrin. The lowest limit detected by the increased sensitivity of the reaction is 3 nmol of an amino acid. Cd2+, Zn2+, and Al3+ depress the color formation due to reaction between amino acids and ninhydrin. When chromatograms of amino acids are first sprayed with aqueous manganese chloride and later with ninhydrin or with ninhydrin solution containing manganese, not only is the sensitivity increased, but the stained spots retain their color for longer periods. 相似文献
10.
The growth capability of Trichoderma harzianum Rifaii Tl was tested on Malt Extract and Czapeks Dox agar containing different concentrations of Cu2+, Zn2+, Mn2+, Fe2+ and Ca2+. The T. harzianum Tl isolate was observed to produce mycelia and spores in various mineral-containing media. It showed the lowest tolerance
to Ca2+ and the highest tolerance to Fe2+. Solubilization capability of T. harzianum Tl for some insoluble minerals via acidification of medium has been tested on MnO2, CuO, Fe2O3 and metallic Zn. T. harzianum Tl was able to solubilize MnO2 and metallic Zn in a liquid medium. 相似文献
11.
The latency phase, growth rate, cell yield and end-products of Lactobacillus sanfranciscensis CB1 were affected by oxygen and the supply of 225 μM Mn2+. Mn2+ was especially related to the highest substrate consumption. Aerobiosis and Mn2+ supply were responsible for the highest superoxide dismutase activity. An auto-inhibitory accumulation of H2O2 meant that the survival of air-grown cells supplied with Mn2+ rapidly decreased during the stationary phase. As shown by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, Mn2+ supply influenced protein expression. As shown by non-denaturating zymograms, Lb. sanfranciscensis CB1 expressed an approximately 12.5-kDa superoxide dismutase, which is probably Mn-dependent. The enzyme was insensitive
to H2O2 treatment, was not induced by the presence of paraquat under aerobic conditions and was relatively stable at pH 4.0. Sourdoughs
that contained high levels of oxygen enhanced cell growth, acidification and acetic acid production by Lb. sanfranciscensis CB1.
Received: 24 July 1998 / Received last revision: 11 November 1998 / Accepted: 13 November 1998 相似文献
12.
Trametes sp. M23, isolated from biosolids compost was found to decompose humic acids (HA). A low N (LN) medium (C/N, 53) provided
suitable conditions for HA degradation, whereas in a high N (HN) medium (C/N, 10), HA was not degraded. In the absence of
Mn2+, HA degradation was similar to that in Mn2+-containing medium. In contrast, MnP activity was significantly affected by Mn2+. Laccase activity exhibited a negative correlation to HA degradation, while LiP activity was not detected. Thus, ligninolytic
enzymes activity could provide only a partial explanation for the HA-degradation mechanism. The decolorization of two dyes,
Orange II and Brilliant Blue R250, was also determined. Similar to HA degradation, under LN conditions, decolorization occurred
independently of the presence of Mn2+. We investigated the possible involvement of a Fenton-like reaction in HA degradation. The addition of DMSO, an OH-radical
scavenger, to LN media resulted in a significant decrease in HA bleaching. The rate of extracellular Fe3+ reduction was much higher in the LN vs. HN medium. In addition, the rate of reduction was even higher in the presence of
HA in the medium. In vitro HA bleaching in non-inoculated media was observed with H2O2 amendment to a final concentration of 200 mM (obtained by 50 mM amendments for 4 days) and Fe2+ (36 mM). After 4 days of incubation, HA decolorization was similar to the biological treatment. These results support our
hypothesis that a Fenton-like reaction is involved in HA degradation by Trametes sp. M23. 相似文献
13.
《Enzyme and microbial technology》2005,36(5-6):785-789
A system comprising laccase and a suitable phenol such as 4-hydroxybenzoic acid (HBA) or synthetic lignin (DHP) exhaustively peroxidized linoleic acid in acetate buffer. The presence of phenols in lignin was essential since an exhaustively methylated preparation of the same lignin did not support peroxidation. The peroxidation rate was greatly enhanced by Mn2+, which was oxidized to Mn3+ by laccase/HBA, whereas H2O2 inhibited strongly due to rapid reduction of Mn3+ by H2O2 with concomitant formation of O2. When acetate was replaced by Mn3+–chelating oxalate or malonate, there was no change in peroxidation rates in the absence of Mn2+, whereas strong inhibition was observed in the presence of Mn2+. In case of malonate part of the inhibition was due to H2O2 formation as a result of Mn3+ reduction by malonate. These findings suggest that laccase may contribute to fungal lipid peroxidation in vivo thus expanding its role in the biodegradation of lignin and other recalcitrant aromatic compounds. 相似文献
14.
L. R. Hatwar S. P. Wankhede S. V. Moharil P. L. Muthal S. M. Dhopte 《Luminescence》2015,30(6):904-909
Pyrophosphates K2AEP2O7 (AE = Ca, Sr) prepared by the classical solid‐state technique and activated with Ce3+ are described. Intense emission was observed in K2AEP2O7 (AE = Ca, Sr). The effect of Mn2+ co‐doping was studied. The broad emission peak of Mn2+ was observed at 534 nm in K2SrP2O7:Ce3+ and at 539 nm in K2CaP2O7:Ce3+, Mn2+. Mn2+ emission was greatly enhanced by addition of the sensitizer Ce3+ due to efficient energy transfer from Ce3+ to Mn2+. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
15.
D. V. Yanykin A. A. Khorobrykh S. A. Khorobrykh N. L. Pshybytko V. V. Klimov 《Photosynthesis research》2013,117(1-3):367-374
It has been shown that removal of manganese from the water-oxidizing complex (WOC) of photosystem II (PSII) leads to flash-induced oxygen consumption (FIOC) which is activated by low concentration of Mn2+ (Yanykin et al., Biochim Biophys Acta 1797:516–523, 2010). In the present work, we examined the effect of transition and non-transition divalent metal ions on FIOC in Mn-depleted PSII (apo-WOC-PSII) preparations. It was shown that only Mn2+ ions are able to activate FIOC while other transition metal ions (Fe2+, V2+ and Cr2+) capable of electron donation to the apo-WOC-PSII suppressed the photoconsumption of O2. Co2+ ions with a high redox potential (E 0 for Co2+/Co3+ is 1.8 V) showed no effect. Non-transition metal ions Ca2+ by Mg2+ did not stimulate FIOC. However, Ca2+ (in contrast to Mg2+) showed an additional activation effect in the presence of exogenic Mn2+. The Ca2+ effect depended on the concentration of both Mn2+ and Ca2+. The Ca effect was only observed when: (1) the activation of FIOC induced by Mn2+ did not reach its maximum, (2) the concentration of Ca2+ did not exceed 40 μM; at higher concentrations Ca2+ inhibited the Mn2+-activated O2 photoconsumption. Replacement of Ca2+ by Mg2+ led to a suppression of Mn2+-activated O2 photoconsumption; while, addition of Ca2+ resulted in elimination of the Mg2+ inhibitory effect and activation of FIOC. Thus, only Mn2+ and Ca2+ (which are constituents of the WOC) have specific effects of activation of FIOC in apo-WOC-PSII preparations. Possible reactions involving Mn2+ and Ca2+ which could lead to the activation of FIOC in the apo-WOC-PSII are discussed. 相似文献
16.
Mn2+ was required for the electron donating reaction from H2O2,but not for that from diphenylcarbazide (DPC), in the PS IIreaction center complex which was prepared from spinach chloroplastsby Triton X-100 extraction. The reaction center complex showeda high activity of 2,6-dichloroindophenol (DCIP) photoreductionin the presence of DPC, but a low activity with H2O2. The H2O2-supportedDCIP photoreduction was suppressed by EDTA and enhanced by asmall amount of Mn2+. Ca2+ and Mg2+ could not replace Mn2+.The activation by Mn2+ and its binding showed two binding sitesof Mn2+ in the reaction center complex, with high (1.5?107 M1)and low (1 ? 106 M1) binding constants. (Received November 8, 1986; Accepted April 10, 1987) 相似文献
17.
《Biochimica et Biophysica Acta (BBA) - Enzymology》1980,611(1):51-60
Product inhibition of lysyl hydroxylase (peptidyllysine, 2-oxoglutarate:oxygen 5-oxidoreductase, EC 1.14.11.4) was studied with succinate, CO2, dehydroascorbate and hydroxylysine-rich polypeptide chains. The product inhibition patterns and addition data are consistent with a reaction mechanism involving an ordered binding of Fe2+, α-ketoglutarate, O2 and the peptide substrate to the enzyme in this order, and an ordered release of the hydroxylated peptide, CO2, succinate and Fe2+, in which Fe2+ need not leave the enzyme during each catalytic cycle and in which the order of release of the hydroxylated peptide and CO2 is uncertain. Ascorbate probably reacts by a substitution mechanism, either after the release of the hydroxylated peptide, CO2 and succinate or after the release of all products, including Fe2+, and dehydroascorbate is released before the binding of Fe2+. It is suggested that the ascorbate reaction is required to reduce either the enzyme-iron complex or the free enzyme, which may be oxidized by a side-reaction during some catalytic cycles, but not the majority. The mechanisms of the prolyl 4-hydroxylase and lysyl hydroxylase reactions are suggested to be identical.Zn2+, several citric acid cycle intermediates, nitroblue tetrazolium and homogentisic acid inhibited lysyl hydroxylase competitively with regard to Fe2+, α-ketoglutarate, O2 and ascorbate respectively, and epinephrine noncompetitively with regard to all cosubstrates. Apparent Ki values are given for the product and other inhibitors. 相似文献
18.
The endo-β-1, 4-xylanase gene xynA from Aspergillus sulphureus, encoded a lack-of-signal peptide protein of 184 amino acids, was de novo synthesized by splicing overlap extension polymerase
chain reaction according to Pichia pastoris protein’s codon bias. The synthetic DNA, composed of 572 nucleotides, was ligated into the downstream sequence of an α-mating
factor in a constitutive expression vector pGAPzαA and electrotransformed into the P. pastoris X-33 strain. The transformed yeast screened by Zeocin was able to constitutively secrete the xylanase in yeast–peptone–dextrose
liquid medium. The heterogenous DNA was stabilized in the strain by 20-times passage culture. The recombinant enzyme was expressed
with a yield of 120 units/mL under the flask culture at 28°C for 3 days. The enzyme showed optimal activity at 50°C and pH 2.4–3.4.
Residual activity of the raw recombinant xylanase was not less than 70% when fermentation broth was directly heated at 80°C
for 30 min. However, the dialyzed xylanase supernatant completely lost the catalytic activity after being heated at 60°C for
30 min. The recombinant xylanase showed no obvious activity alteration by being pretreated with Na2HPO4-citric acid buffer of pH 2.4 for 2 h. The xylanase also showed resistance to certain metal ions (Na+, Mg2+, Ca2+, K+, Ba2+, Zn2+, Fe2+, and Mn2+) and EDTA. These biochemical characteristics suggest that the recombinant xylanase has a prospective application in feed
industry as an additive. 相似文献
19.
Mohammad Mahdi Najafpour 《Origins of life and evolution of the biosphere》2011,41(3):237-247
In this paper a few calcium-manganese oxides and calcium-manganese minerals are studied as catalysts for water oxidation.
The natural mineral marokite is also studied as a catalyst for water oxidation for the first time. Marokite is made up of
edge-sharing Mn3+ in a distorted octahedral environment and eight-coordinate Ca2+ centered polyhedral layers. The structure is similar to recent models of the oxygen evolving complex in photosystem II. Thus,
the oxygen evolving complex in photosystem II does not have an unusual structure and could be synthesized hydrothermally.
Also in this paper, oxygen evolution is studied with marokite (CaMn2O4), pyrolusite (MnO2) and compared with hollandite (Ba0.2Ca0.15K0.3Mn6.9Al0.2Si0.3O16), hausmannite (Mn3O4), Mn2O3.H2O, CaMn3O6.H2O, CaMn4O8.H2O, CaMn2O4.H2O and synthetic marokite (CaMn2O4). I propose that the origin of the oxygen evolving complex in photosystem II resulted from absorption of calcium and manganese
ions that were precipitated together in the archean oceans by protocyanobacteria because of changing pH from ~5 to ~8-10.
As reported in this paper, amorphous calcium-manganese oxides with different ratios of manganese and calcium are effective
catalysts for water oxidation. The bond types and lengths of the calcium and manganese ions in the calcium-manganese oxides
are directly comparable to those in the OEC. This primitive structure of these amorphous calcium-manganese compounds could
be changed and modified by environmental groups (amino acids) to form the oxygen evolving complex in photosystem II. 相似文献
20.
Joshua Allen Hayden Michael P. Hendrich 《Journal of biological inorganic chemistry》2010,15(5):729-736
DNA-binding proteins from nutrient-starved cells (DPS) protect cells from oxidative stress by removing H2O2 and iron. A new class of DPS-like proteins has recently been identified, with DPS-like protein from Sulfolobus solfataricus (SsDPS) being the best characterized to date. SsDPS protects cells from oxidative stress and is upregulated in response to
H2O2 but also in response to iron depletion. The ferroxidase active site of SsDPS is structurally similar to the active sites
of manganese catalase and rat liver arginase. The present work shows that the ferroxidase center in SsDPS binds two Mn2+ ions with K
D = (1/K
1
K
2)1/2 = 48(3) μM. The binding constant of the second Mn2+ is significantly higher than that of the first, inducing dinuclear Mn(II) cluster formation for all but the lowest concentrations
of added Mn2+. In competition experiments, equimolar amounts of Fe2+ were unable to displace the bound manganese. EPR spectroscopy of the Mn2
2+ cluster showed signals comparable to those of other characterized dimanganese clusters. The exchange coupling for the cluster
was determined, J = −1.4(3) cm−1 (H = −2JS
1
S
2), and is within the range expected for a μ1,1-carboxylato bridge between the manganese ions. Manganese-bound SsDPS showed catalase activity at a rate 10–100 times slower
than for manganese catalases. EPR spectra of SsDPS after addition of H2O2 showed the appearance of an intermediate in the reaction with H2O2. 相似文献