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1.
The inactivation temperature for Hill activity and for the long-lived delayed fluorescence of isolated Pisum sativum L. chloroplasts was found to depend on pH, the maximal value being in the pH region 5–7. Salts increase the inactivation temperature by 4–7°C. Effects of D2O and some other substances that modify the thermostability of chloroplasts are dependent on pH. It is concluded that thermal denaturation of proteins is the most probable mechanism for heat inactivation of chloroplasts.Abbreviations Hepes
4-(2-hydroxymethyl)-1-piperazineethane sulfonic acid
- Tris
2-amino-2-(hydroxymethyl)-1,3-propanediol 相似文献
2.
Long lasting batch cultures of Azospirillum brasilense SP 7 ATCC 29145 grown in liquid malate medium for 8–14 days without any fixed nitrogen source exhibited a biphasic nitrogenase activity, when incubated under gas atmospheres of 99.0% N2 and 1.0% O2 or 99.5% N2 and 0.5% O2 respectively. Maximum specific nitrogenase activity was 1100 nmol C2H4·mg protein-1·h-1. Poly-3-hydroxybutanoic acid (PHBA) synthesis and growth of the cells also showed two phases. Maxima and minima of glutamine synthetase activity developed synchronously with nitrogenase activity, whereas those of glutamate dehydrogenase and alanine aminotransferase were reverse. During a 192 h period of growth protein increased 3–4-fold and PHBA 25 fold. At maximum accumulation of the polymer the PHBA-nitrogen ratio was 6:1 or 8:1. Azospirillum brasilense was also able to fix nitrogen on agar surfaces exposed to air, but nitrogen fixation was monophasic under these conditions during a 14 d period. Specific nitrogenase activity was dependent on the type and concentration of the source of fixed nitrogen (leucine, ammonia) in solidified media. With 1 mM leucine maximum specific nitrogenase activity was 110 nmol C2H4·mg protein-1·h-1.Non-Standard Abbreviations PHBA
poly-3-hydroxybutanoic acid
- TAPS
tris(hydroxymethyl)methylaminopropane sulfonic acid
- TES
N-tris(hydroxymethyl)methyl-2-aminoethane sulfonic acid
- TRICINE
N-tris(hydroxymethyl)methylglycine
- TRIS
tris(hydroxymethyl)aminomethane 相似文献
3.
Phosphatase activities were measured in preparations of vacuoles isolated from storage roots of red beet (Beta vulgaris L.). The vacuoles possessed both acid phosphatase and ATPase activities which could be distinguished by their susceptibility to inhibition by low concentrations of ammonium molybdate [(NH4)6Mo7O24·4H2O]. The acid phosphatase was completely inhibited by 100 M ammonium molybdate but the ATPase was unaffected. The acid phosphatase was a soluble enzyme which hydrolysed a large number of phosphate esters and had a pH optimum of 5.5. In contrast, the ATPase was partially membrane-bound, had a pH optimum of 8.0 and hydrolysed ATP preferentially, although it was also active agianst PPi, GTP and GDP. At pH 8.0 both the ATPase and PPase activities were Mg2+-dependent and were further stimulated by KCl. The ATPase and PPase activities at pH 8.0 may be different enzymes. The recovery and purification of the ATPase during vacuole isolation were determined. The results indicate that the Mg2+-dependent, KCl-stimulated ATPase activity is not exclusively associated with vacuoles.Abbreviations BSA
bovine serum albumen
- MES
2-(N-Morpholino)ethanesulphonic acid
- MOPS
3-(N-Morpholino)propanesulphonic acid
- Na2EDTA
ethylenediaminetetra-acetic acid, disodium salt
- Pi
inorganic phosphate
- PPi
inorganic pyrophosphate
- PPase
inorganic pyrophosphatase
- TCA
trichloroacetic acid
- TES
N-tris(hydroxymethyl)methyl-2-amino-ethanesulphonic acid
- Tris
tris(hydroxymethyl)methylamine 相似文献
4.
Peter van der Meijden Chris van der Drift Godfried D. Vogels 《Archives of microbiology》1984,138(4):360-364
The conversion of methanol by cell-free extracts of the acetogenic bacterium Eubacterium limosum was studied. Incubation of mixed cell-free extracts of both E. limosum and Methanobacterium formicicum resulted in methane formation from methanol in the presence of ATP and 2-mercaptoethanesulfonic acid. The separate extracts were not able to perform this reaction. Addition of ferredoxin obtained from Methanosarcina barkeri to the mixed extracts resulted in increased methane formation. The enzyme, responsible for methanol binding in cell-free extract of E. limosum, was inactivated by FAD under N2 and exhibited maximal activity under an atmosphere of H2. This enzyme contains a firmly bound cobalamin which was methylated by methanol in the presence of ATP. It was demethylated in the presence of methylcobalamin: coenzyme M methyltransferase obtained from M. barkeri under concomitant formation of methylated coenzyme M. These properties are similar to those of methanol: 5-hydroxybenzimidazolylcobamide methyltransferase from M. barkeri. It was proposed that methylotrophic acetogens and methylotrophic methanogens use similar enzymes in the first step of methanol conversion.Abbreviations HS-CoM
2-mercaptoethanesulfonic acid
- CH3S-CoM
2-(methylthio)ethanesulfonic acid
- BrES
2-bromoethanesulfonic acid
- TES
N-tris(hydroxymethyl)-methyl-2-aminoethanesulfonic acid
- MT1
methanol: 5-hydroxybenzimidazolylcobamide methyltransferase
- MT2
methylcobalamin
- HS-CoM
methyltransferase
- DMBI
5,6-dimethylbenzimidazole and HBI, 5-hydroxybenzimidazole, are -ligands of corrinoids
- (S-CoM)2
2,2-dithiodiethanesulfonic acid 相似文献
5.
Summary NADP-dependent glutamate dehydrogenase from Dictyostelium discoideum was purified 9300 fold with a yield of 4.6%. The enzyme is a hexamer of apparent molecular weight 294 kDa on Sephacryl S400 and a subunit molecular weight of 52 kDa as determined by SDS gel electrophoresis. The apparent KmS for -ketoglutarate, NADPH and NH
inf4
sup+
are 1.2 mM, 9.7 µM and 2.2 mM respectively, and the purified enzyme has a broad pH optimum with a peak at pH 7.75. GTP has a slight stimulatory effect (22% at 83 µM) as does ADP (11% at 1 mM), and AMP is slightly inhibitory (9% at 1 mM) whereas adenosine, ATP and cAMP have little or no effect. Neither the Zn2+ chelating compound 1,10-phenanthroline nor EDTA have any effect on the enzyme while p-hydroxymercuribenzoic acid inhibits enzyme activity (50% at 80 µM) yet N-ethylmaleimide does not.In addition, the NADP-GDH activity varies little during the various stages of morphogenesis.Abbreviations EDTA
Ethylenediamine Tetraacetic Acid
- Tris
Tris(hydroxymethyl)aminomethane
- Bis-tris
bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane
- TRITON X-100
iso-octylphenoxypoly-ethoxyethanol
-
pHMB
p-Hydroxymercuribenzoic acid 相似文献
6.
Membrane vesicles were isolated from mesophyll cells of Mesembryanthemum crystallinum in the C3 state and in the crassulacean acid metabolism (CAM) state. The distribution of ATP-hydrolysis and H+-transport activities, and the activities of hydroxypyruvate reductase and Antimycin-insensitive cytochrome-c-reductase on continuous sucrose gradients was studied. For isolations carried out routinely a discontinuous sucrose gradient (24%/37%/50%) was used. Nitrate-sensitive ATP-hydrolysis and H+-transport activities increased several-fold during the transition from C3 photosynthesis to CAM. Nitrate-sensitive ATPase showed a substrate preference for ATP with an apparent Km (MgATP2-) of 0.19–0.37 mM. In both C3 and CAM states the ATPase showed a concentration-dependent stimulation by the anions chloride and malate. However, the pH optima of the two states were different: the ATPase of C3-
M. crystallinum had an optimum of pH 7.4 and that of CAM-M. crystallinum an optimum of pH 8.4. The optical probe oxonol-VI was used to demonstrate the formation of MgATP2--dependent electric-potential gradients in tonoplast vesicles.Abbreviations Bistris-Pronane
1,3-bis [tris(hydroxymethyl)-methylaminol propane
- CAM
Crassulacean acid metabolism
- DIDS
4,4-dilsothiocyano-2,2-stilbene disulfonic acid:
- DTT
dithiothreitol
- ER
endoplasmic reticulum
- Hepes
4-(2-hydroxyethyl)-1-piperazineethane sulfonic acid
- HPR
hydroxypyruvate reductase
- IDPase
inosine 5-diphosphatase
- OX-VI
oxonol VI
- Tris
2-amino-2-(hydroxymethyl)-1,3-propanediol 相似文献
7.
After preheating of Amaranthus chloroplasts at elevated temperatures (up to 45°C), the chlorophyll a fluorescence level under low excitation light rises as compared to control (unheated) as observed earlier in other chloroplasts (Schreiber U and Armond PA (1978) Biochim Biophys Acta 502: 138–151). This elevation of heat induced fluorescence yield is quenched by addition of 0.1 mM potassium ferricyanide, suggesting that with mild heat stress the primary electron acceptor of photosystem II is more easily reduced than the unheated samples. Furthermore, the level of fluorescence attained after illumination of dithionite-treated samples is independent of preheating (up to 45°C). Thus, these experiments indicate that the heat induced rise of fluorescence level at low light can not be due to changes in the elevation in the true constant F0 level, that must by definition, be independent of the concentration of QA. It is supposed that the increase in the fluorescence level by weak modulated light is either partly associated with dark reduction of QA due to exposure of chloroplasts to elevated temperature or due to temperature induced fluorescence rise in the so called inactive photosystem II centre where QA are not connected to plastoquinone pool. In the presence of dichlorophenyldimethylurea the fluorescence level triggered by weak modulated light increases at alkaline pH, both in control and heat stressed chloroplasts. This result suggests that the alkaline pH accelerates electron donation from secondary electron donor of photosystem II to QA both in control and heat stressed samples. Thus the increase in fluorescence level probed by weak modulated light due to preheating is not solely linked to increase in true F0 level, but largely associated with the shift in the redox state of QA, the primary stable electron acceptor of photosystem II.Abbreviations ADRY
Acceleration of Deactivation of Reaction of Enzyme Y
- CCCP
Carbonyl cyanide 4-(trifluoromethoxy)-phenylhydrazone
- Chl
Chlorophyll
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- FeCN
potassium ferricyanide
- HEPES
4-(2-hydroxy ethyl)-1-piperazine ethane sulfonic acid
- LHCP
Light harvesting chlorophyll protein
- MES
(4-morpholine ethane sulfonic acid)
- PS
photosystem
- QA and QB
first and second consecutive electron acceptors of photosystem II
- TES
(2-[tris(hydroxymethyl)-methylamino]-1-ethanesulfonic acid) sulfonic acid
- TRICINE
N-[tris(hydroxymethyl)methyl] glycine 相似文献
8.
Mitochondria isolated from spinach leaves (Spinacia oleracea L.) and potato tubers (Solanum tuberosum L.) were partly injured when subjected to freezing for 2 to 4 h at-25°C in salt solutions in the absence of cryoprotectants. Damage was manifested by the inactivation of respiratory properties and increase in the permeability of the mitochondrial membranes. Decrease in respiratory control indicated that the control mechanism of the electron transport chain was influenced by freezing. Oxidative phosphorylation was only slightly more affected than electron transport. The inactivation of the membrane systems was caused by an increase in the concentration of membrane-toxic solutes. This was confirmed by treatment of the organelles at 0°C in solutions of high salt concentrations. When sugar was present in the course of freezing, mitochondria were partly or completely protected. On a molar basis, sucrose was more effective in membrane protection than glucose. Under certain conditions amino acids, e.g., proline and hydroxyproline, also stabilized isolated mitochondria during freezing.Abbreviations BSA
bovine albumin
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethane sulfonic acid
- MOPS
2-N-morpholinopropane sulfonic acid
- PVP
polyvinyl pyrrolidone
- RC
respiratory control
- Tris
tris (hydroxymethyl) aminomethane 相似文献
9.
A trimethylamine:2-mercaptoethanesulfonate (HS-coenzyme M) methyltransferase has been shown to be present in trimethylamine-grown cells but not in methanol-grown cells of Methanosarcina barkeri. The transfer of one methyl group was catalyzed by this enzyme so that dimethylamine and methyl-S-coenzyme M were the products. Enzyme activity required the presence of ATP and preincubation of the protein solution under H2. Fifty percent of the maximum activity was obtained under N2 in the presence of NAD(P)H plus dithioerythritol.Abbreviations HS-coenzyme M
2-mercaptoethanesulfonic acid
- methyl-S-coenzyme M
2-(methylthio)ethanesulfonic acid
- TES
N-tris (hydroxymethyl)-methyl-2-aminoethanesulfonic acid
- DTE
1,4-dithioerythritol
- BrES
2-bromoethanesulfonic acid
- DTT
1,4-dithiothreotol 相似文献
10.
Helen Baubichon-Cortay Pierre Broquet Pascal George Pierre Louisot 《Glycoconjugate journal》1989,6(1):115-127
We have studied the amino-acid residues involved in the catalytic activity of two distinct brain sialyltransferases acting on fetuin and asialofetuin. These two enzymes were strongly inhibited byN-bromosuccinimide, a specific blocking reagent for tryptophan residues. This result suggests the involvement of such residues in the catalytic process of the two sialytransferases. Furthermore, chemical modifications by various sulfhydryl reagents led to a strong inhibition of the fetuin sialyltransferase while the asialofetuin sialyltransferase was only slightly inhibited. For a more thorough understanding of the thiol inactivation mechanism of the fetuin sialyltransferase, we studied in more detail the reactivity of this enzyme with NEM (N-ethylmaleimide), an irreversible reagent. The time-dependent inactivation followed first-order kinetics and these kinetic data afforded presumptive evidence for the binding of 1 mol NEM per mol of enzyme. Only CMP-NeuAc protected the enzyme against NEM inactivation effectively. MnCl2 did not enhance the protective effect of CMP-NeuAc. The modifications of the fetuin sialyltransferase kinetic parameters by NEM showed a competitive mechanism between NEM and CMP-NeuAc. The results suggest the involvement of a sulfhydryl residue in or near the nucleotide-sugar binding may induce a change in conformation of the protein, leading to a decreased accessibility of this thiol group located near the nucleotide-sugar binding site). This SH group, is essential to the enzyme activity, which is not the case for the asialofetuin sialyltransferase.Abbreviations
p-CMB
p-chloromercuribenzoic acid
- CPDS
6,6-dithiodinicotinic acid carboxypyridine disulfide
- DTNB
5,5-dithiobis-(2-nitrobenzoic acid)
- NEM
N-ethylmaleimide
- DTT
dithiothreitol
- Mes
2-(N-morpholino)ethane sulfonic acid
- NeuAc
N-acetylneuraminic acid 相似文献
11.
Nitrogenase from soybean bacteroids was purified and used to study NO
2
–
effects either as unfractionated enzyme or as reconstituted enzyme from separated nitrogenase components I and II. Partially purified enzyme was strongly inhibited by nitrite at concentrations less than 0.1 mM. This inhibition was typically referred to as competitive with an inhibition constant (K
i) for NO
2
–
which was 5.2 mM. Kinetics studies showed an abnormally low apparent constant of association between enzyme and NO
2
–
(k
a=60 M-1·s-1). Nitrite appeared to bind to the MoFe protein, without any effect on Fe component, giving a completely reversible inhibition. Nitrite was found not to be an alternative substrate for nitrogenase.Abbreviations TES
N-tris (hydroxymethyl) methyl-2-aminoethane sulfonic acid
- PPG
Polypropylene glycol 相似文献
12.
Maria Rova Lars-Gunnar Franzén Per-Olof Fredriksson Stenbjörn Styring 《Photosynthesis research》1994,39(1):75-83
The psbP gene product, the so called 23 kDa extrinsic protein, is involved in water oxidation carried out by Photosystem II. However, the protein is not absolutely required for water oxidation. Here we have studied Photosystem II mediated electron transfer in a mutant of Chlamydomonas reinhardtii, the FUD 39 mutant, that lacks the psbP protein. When grown in dim light the Photosystem II content in thylakoid membranes of FUD 39 is approximately similar to that in the wild-type. The oxygen evolution is dependent on the presence of chloride as a cofactor, which activates the water oxidation with a dissociation constant of about 4 mM. In the mutant, the oxygen evolution is very sensitive to photoinhibition when assayed at low chloride concentrations while chloride protects against photoinhibition with a dissociation constant of about 5 mM. The photoinhibition is irreversible as oxygen evolution cannot be restored by the addition of chloride to inhibited samples. In addition the inhibition seems to be targeted primarily to the Mn-cluster in Photosystem II as the electron transfer through the remaining part of Photosystem II is photoinhibited with slower kinetics. Thus, this mutant provides an experimental system in which effects of photoinhibition induced by lesions at the donor side of Photosystem II can be studied in vivo.Abbreviations Chl
chlorophyll
- DCIP
2,6-dichlorophenolindophenol
- DPC
2,2-diphenylcarbonic dihydrazide
- HEPES
4-(2-hydroxyethyl)-1-piperazinethanesulfonic acid
- P680
the primary electron donor to PS II
- PpBQ
phenyl-p-benzoquinone
- PS II
Photosystem II
- QA
the first quinone acceptor of PS II
- QB
the second quinone acceptor of PS II
- SDS
sodium dodecyl sulfate
- Tris
tris(hydroxymethyl)aminomethane
- TyrD
accessory electron donor on the D2-protein
- TyrZ
tyrosine residue, acting as electron carrier between P680 and the water oxidizing system 相似文献
13.
Summary Plasma membranes of maize (Zea mays L., cv. Sil Anjou 18) roots were isolated by aqueous two-phase partitioning. Multi elemental analysis by proton induced X-ray emission (PIXE) was used for the investigation of elemental composition of plasma membranes. Fe, Cu, and Zn as well as P, S, and Ca were identified. We did not find significant amounts of V, Mn, Se, Mo, or W.Abbreviations EDTA
ethylenediaminetetraacetic acid
- HCF III
hexacyanoferrate III (ferricyanide, K3[FeCN6])
- Hepes
2-[4-(2-hydroxyethyl)-1-piperazine]-ethanesulfonic acid
- PIXE
proton induced X-ray emission (proton microprobe)
- STA
siliciotungstic acid
- Tris
tris (hydroxymethyl)aminomethane 相似文献
14.
An improved procedure for the isolation of the cytochromeb
6/f complex from spinach chloroplasts is reported. With this preparation up to tenfold higher plastoquinol-plastocyanin oxidoreductase activities were observed. Like the complex obtained by our previous procedure, the complex prepared by the modified way consisted of five polypeptides with apparent molecular masses of 34, 33, 23, 20, and 17 kD, which we call Ia, Ib, II, III, and IV, respectively. In addition, one to three small components with molecular masses below 6 kD were now found to be present. These polypeptides can be extracted with acidic acetone. Cytochromef, cytochromeb
6, and the Rieske Fe-S protein could be purified from the isolated complex and were shown to be represented by subunits Ia + Ib, II, and III, respectively. The heterogeneity of cytochromef is not understood at present. Estimations of the stoichiometry derived from relative staining intensities with Coomassie blue and amido black gave 1:1:1:1 for the subunits Ia + Ib/II/III/IV, which is interesting in of the presence of two cytochromesb
6 per cytochromef. Cytochromef titrated as a single-electron acceptor with a pH-independent midpoint potential of +339 mV between pH 6.5 and 8.3, while cytochromeb
6 was heterogeneous. With the assumption of two components present in equal amounts, two one-electron transitions withE
m(1)=–40 mV andE
m(2)=–172 at pH 6.5 were derived. Both midpoint potentials were pH-dependent.Abbreviation Tris
tris(hydroxymethyl)aminomethane
- SDS
sodium dodecylsulfate
- SDS-PAGE
SDS polyacrylamide gel electrophoresis
- MES
2-(N-morpholino)ethanesulfonic acid 相似文献
15.
Characterization by peptide mapping and amino acid analysis of the two major pyrenoid polypeptides from the brown alga Pilayella littoralis shows that they are very similar to the subunits of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) from this alga. The observed similarities are discussed in relation to previous pyrenoid protein characterization from members of the Chlorophyceae.Abbreviations DTT
dithiothreitol
- EDTA Na2
ethylenediamine tetraacetic acid (disodium salt)
- PMFS
phenylmethylsul-phonylfluoride
- PVPP
polyvinylpyrrolidone
- RuBP
ribulose-1,5-bisphosphate
- RuBPCase
ribulose-1,5-bisphosphate carboxylase
- SDS
sodium dodecyl sulphate
- SDS-PAGE
sodium dodecyl sulphate polyacrylamide gel electrophoresis
- TRIS
2-amino-2-(hydroxymethyl) propane-1,3-diol
- TPCK
L-1-tosylamido-2-phenylethylchoromethyl ketone 相似文献
16.
Separation and purification of the tonoplast ATPase and pyrophosphatase from plants with constitutive and inducible Crassulacean acid metabolism 总被引:7,自引:0,他引:7
Tonoplast vesicles were isolated from Kalanchoe daigremontiana Hamet et Pierrer de la Bâthie and Mesembryanthemum crystallinum L., exhibiting constitutive and inducible crassulacean acid metabolism (CAM), respectively. Membrane-bound proteins were detergent-solubilized with 2% of Triton X-100. During CAM induction in M. crystallinum, ATPase activity increases four-fold, whereas pyrophosphatase activity decreases somewhat. With all plants, ATPase and pyrophosphatase could be separated by size-exclusion chromatography (SEC, Sephacryl S 400), and the ATPase was further purified by diethylaminoethyl-ion-exchange chromatography. Sodium-dodecyl-sulfate electrophoresis of the SEC fractions from K. daigremontiana containing maximum ATPase activity separates several protein bands, indicating subunits of 72, 56, 48, 42, 28, and 16 kDa. Purified ATPase from M. crystallinum in the C3 and CAM states shows a somewhat different protein pattern. With M. crystallinum, an increase in ATP-hydrolysis and changes in the subunit composition of the native enzyme indicate that the change from the C3 to the CAM state is accompanied by de-novo synthesis and by structural changes of the tonoplast ATPase.Abbreviations CAM
Crassulacean acid metabolism
- DTT
dithiothreitol
- kDa
kilodalton
- PAGE
polyacrylamide gel electrophoresis
- PPiase
pyrophosphatase
- SEC
size exclusion chromatography
- SDS
sodium dodecyl sulfate
- Tris
2-amino-2-(hydroxymethyl)-1,3-propanediol 相似文献
17.
The uptake of sucrose against a concentration gradient into the dextran-impermeable [3H]H2O space of red beet (Beta vulgaris L.) vacuoles has been studied using silicone-layer-filtering centrifugation on both fluorometric and 14C-measurement of sucrose. Sucrose transport into vacuoles proceeds partly by an active transport system and partly by passive permeation. The K
M(20°C) for active sucrose uptake was found to be about 22 mM and the V
Max(20°C) was about 174 nmol sucrose x (unit betacyanin)-1 x h-1. The temperature dependency of sucrose transport appears to have an activation energy of 35,0 KJ×mol-1. Among various mono-, di-, and trisaccharides tested, raffinose acts as a competitive inhibitor of sucrose uptake.Abbreviations EDTA
ethylenediamine tetraacetic acid
- fr. wt.
fresh weight
- Tris
tris-(hydroxymethyl)-aminomethan 相似文献
18.
Dirk H. Engels Alexandra Lott Georg H. Schmid Elfriede K. Pistorius 《Photosynthesis research》1994,42(3):227-244
The previously constructed MSP (manganese stabilizing protein-psbO gene product)-free mutant of Synechococcus PCC7942 (Bockholt R, Masepohl B and Pistorius E K (1991) FEBS Lett 294: 59–63) and a newly constructed MSP-free mutant of Synechocystis PCC6803 were investigated with respect to the inactivation of the water-oxidizing enzyme during dark incubation. O2 evolution in the MSP-free mutant cells, when measured with a sequence of short saturating light flashes, was practically zero after an extended dark adaptation, while O2 evolution in the corresponding wild type cells remained nearly constant. It could be shown that this inactivation could be reversed by photoactivation. With isolated thylakoid membranes from the MSP-free mutant of PCC7942, it could be demonstrated that photoactivation required illumination in the presence of Mn2+ and Ca2+, while Cl– addition was not required under our experimental conditions. Moreover, an extended analysis of the kinetic properties of the water-oxidizing enzyme (kinetics of the S3(S4)S0 transition, S-state distribution, deactivation kinetics) in wild type and mutant cells of Synechococcus PCC7942 and Synechocystis PCC6803 was performed, and the events possibly leading to the reversible inactivation of the water-oxidizing enzyme in the mutant cells are discussed. We could also show that the water-oxidizing enzyme in the MSP-free mutant cells is more sensitive to inhibition by added NH4Cl-suggesting that NH3 might be a physiological inhibitor of the water oxidizing enzyme in the absence of MSP.Abbreviations Chl
chlorophyll
- DCBQ
2,6-Dichloro-p-benzoquinone
- MSP
manganese stabilizing protein (psbO gene product)
- PS II
Photosystem II
- WOE
water oxidizing enzyme
- WT
wild type
This paper is dedicated to Prof. Dr. Bernard Axelrod on the occasion of his 80th birthday 相似文献
19.
The crude extracellular cellulase from Clostridium thermocellum was oxidatively inactivated by air and inhibited by sulfhydryl reagents. Activity-loss was prevented and reversed by the addition of a high concentration (10 mM) dithiothreitol (DDT) at zero time and up to 24 h respectively. In the presence of a low concentration (0.4 mM) of DTT, the enzyme was more rapidly inactivated than in air alone. This was probably due to autoxidation of the low DTT concentration to H2O2 as shown by its prevention by a high DTT concentration, exclusion of air, or catalase; and by the oxidative inactivation of the enzyme by H2O2. The inactivation by H2O2 could be prevented by a high concentration of DTT but not by air exclusion. EDTA protected the enzyme from inactivation in air by a low concentration of DTT or by H2O2. This is presumably due to the role of metals in oxidation of SH groups. Furthermore, copper (5 M) also caused inactivation and this was prevented by the presence of a high DTT concentration. Even in the protective atmosphere of a high DTT concentration, cellulase was inactivated by certain apolar chelating agents such as o-phenanthroline and -1-dipyridyl, such inactivation being preventable by the prior incubation of the chelator with a mixture of Fe2+ and Fe3+. These data suggest that the clostridial cellulase, unlike the enzyme from aerobic fungi, contains essential sulfhydryl groups and is stimulated by iron. The endo--glucanase component of the cellulase complex was not susceptible to oxidative inactivation.Abbreviations DTT
dithiothreitol
- CMC
carboxymethylcellulose
- DTNB
5,5-dithiobis-(2-nitrobenzoic acid)
- NEM
N-ethylmaleimide
-
p-CMB
p-chloromercuribenzoic acid 相似文献
20.
The effect of the nitrogen source on nitrate reductase and nitrite reductase synthesis has been studied in several filamentous dinitrogen-fixing cyanobacteria belonging to the genera Anabaena, Nostoc and Calothrix. Nitrate and nitrite uptake were also studied. High levels of both nitrate reductase and nitrite reductase were found only in the presence of nitrate or nitrite, as long as ammonium was absent from the culture medium. On the other hand, whereas nitrate uptake is an active process, two components, diffusion of nitrous acid and active transport of nitrite, appear to contribute to nitrite uptake.Abbreviations DCCD
N,N-dicyclohexylcarbodiimide
- MOPS
3-(N-morpholino)propanesulfonic acid
- TES
N-tris(hydroxymethyl)methyl-2-aminoethane-sulfonic acid
- Tricine
N-tris(hydroxymethyl)methylglycine 相似文献