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1.
J. Kelley Bentley Peter W. Reed 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,678(2):238-244
All of the common cytochalasins activate superoxide anion release and exocytosis of β-N-acetylglucosaminidase and lysozyme from guinea-pig polymorphonuclear leukocytes (neutrophils) incubated in a buffered sucrose medium. Half-maximal activation of both processes is produced by approx. 2 μM cytochalasin A, C >μM cytochalasin B ? 4–5 μM cytochalasin D, E. While maximal rates of O2? release and extents of exocytosis require extracellular calcium (1–2 mM), replacing sucrose with monovalent cation chlorides is inhibitory to neutrophil activation by cytochalasins. Na+, K+ or choline inhibited either cytochalasin B- or E-stimulated O2? production with IC50 values of 5–10 mM and inhibition occurs whether Cl?, NO3? or SCN? is the anion added with Na+ or K+. Release of β-N-acetylglucosaminidase in control or cytochalasin B-stimulated cells is inhibited by NaCl (IC50 ≈ 10 mM), while cytochalasin E-stimulated exocytosis is reduced less and K+ or choline chloride are ineffective in inhibiting either cytochalasin B- or E-stimulated exocytosis. Release of β-glucuronidase, myeloperoxidase or acid phosphatase from neutrophils incubated in buffered sucrose is not stimulated by cytochalasin B. Stimulation of either O2? or β-N-acetylglucosaminidase release by low concentrations of cytochalasin A is followed by inhibition of each at higher concentrations. It appears that all cytochalasins can activate both NAD(P)H oxidase and selective degranulation of neutrophils incubated in salt-restricted media and that differential inhibition of these two processes by monovalent cations and/or anions is produced at some step(s) subsequent to cytochalasin interaction with the cell. 相似文献
2.
Xiuyun Ye Shigeru Yoshida T. B. Ng 《The international journal of biochemistry & cell biology》2000,32(11-12)
A mild and rapid method is described for isolating various milk proteins from bovine rennet whey. β-Lactoglobulin from bovine rennet whey was easily adsorbed on and desorbed from a weak anion exchanger, diethylaminoethyl-Toyopearl. However, α-lactalbumin could not be adsorbed onto the resin. α-Lactalbumin and β-lactoglobulin from rennet whey could also be adsorbed and separated using a strong anion exchanger, quaternary aminoethyl-Toyopearl. The rennet whey was passed through a strong cation exchanger, sulphopropyl-Toyopearl, to separate lactoperoxidase and lactoferrin. α-Lactalbumin and β-lactoglobulin were adsorbed onto quaternary aminoethyl-Toyopearl. α-Lactalbumin was eluted using a linear (0–0.15 M) concentration gradient of NaCl in 0.05 M Tris–HCl buffer (pH 8.5). Subsequently, β-lactoglobulin B and β-lactoglobulin A were eluted from the column with 0.05 M Tris–HCl (pH 6.8), using a linear (0.1–0.25 M) concentration gradient of NaCl. The yields were 1260 mg α-lactalbumin, 1290 mg β-lactoglobulin B and 2280 mg β-lactoglobulin A from 1 l rennet whey. 相似文献
3.
Ulrich Weser Karl-Heinz Sellinger Edmund Lengfelder Walther Werner Joachim Strähle 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,631(2):232-245
The copper complex of indomethacin (1-(p-chlorobenzoyl)-5-methoxy-2-methyl-indole acetate), a common anti-inflammatory drug, was prepared and characterized. Crystal structure determination revealed the dimeric form of the 1:2 complex, namely Cu2(indomethacin)4 · L2, in the unit cell. Suprisingly, the copper-copper distance (263 pm) was very close to metallic copper (256 pm). The two coordination sites in the copper-copper axis can be readily replaced by superoxide. An intriguing similarity to Cu2(acetate)4 was seen.Due to the lipophilic nature of the indomethacin ligand, this copper complex reacted with superoxide in aprotic solvents. The superoxide dismutating activity was successfully demonstrated in Me2SO/water and acetonitrile/water mixtures using the nitro-blue tetrazolium assay and pulse radiolysis. The second-order rate constant of 6 · 109 M?1 · s?1 in strictly aqueous systems dropped only slightly to 1.1 · 109 M?1 · s?1 when aprotic solvents were used. This is the fastest rate constant ever observed for a copper-dependent dismutation of superoxide. The KO2-induced lipid peroxidation in both erythrocytes and liver microsomes was suppressed by 70% in the presence of 1 · 10?10 mol · ml?1 of Cu2(indomethacin)4. The inhibitory action dropped to 25% when Cu2Zn2superoxide dismutase was employed. The formation of copper · indomethacin in rat serum after administration of indomethacin was shown in vitro and in vivo. 相似文献
4.
《Free radical research》2013,47(1):287-296
A full understanding of enzyme-substrate interactions requires a detailed knowledge of their structural basis at atomic resolution. Crystallographic and biochemical data have been analyzed with coupled computational and computer graphic approaches to characterize the molecular basis for recognition of the superoxide anion substrate by Cu. Zn superoxide dismutase (SOD). Detailed analysis of the bovine SOD structure aligned with SOD sequences from 15 species provides new results concerning the significance and molecular basis for sequence conservation. Specific roles have been assigned for all 23 invariant residues and additional residues exhibiting functional equivalence. Sequence invariance is dominated by 15 residues that form the active site stcreochemistry. supporting a primary biological function of superoxide dismutation. Using data from crystallographic structures and site-directed mutants, we are testing the role of individual residues in the active site channel, including (in human SOD) Glu132, Glu133, Lys136, Thr137, and Arg 143. Electrostatic calculations incorporating molecular flexibility suggest that the region of positive electrostatic potential in and over the active site channel above the Cu ion sweeps through space during molecular motion to enhance the facilitated diffusion responsible for the enzyme's rapid catalytic rate. 相似文献
5.
Aquaspirillum magnetotacticum MS-1 cells cultured microaerobically (dissolved O2 tension 1% of saturation), expressed proteins with superoxide dismutase (SOD) activity. The majority (roughly 95%) of total cell superoxide dismutase activity was located in the cell periplasm with little or no activity in the cell cytoplasm. Irontype SOD (FeSOD) contributed 88% of the total activity activity detected, although a manganese-type SOD (MnSOD) was present in the periplasm as well. Cells cultured at a higher dissolved O2 tension (10% of saturation) expressed increased activity of the MnSOD relative to that of the FeSOD. 相似文献
6.
T.S. Nedeva V.A. Savov A.V. Kujumdzieva-Savova E.R. Davidov 《FEMS microbiology letters》1993,107(1):49-52
Abstract A screening procedure for highly thermostable yeast superoxide dismutase was developed. Growth yields at various temperatures were estimated for ten mesophilic and thermotolerant strains, belonging to the genera Saccharomyces, Kluyveromyces and Pichia . Higher yields at 45°C were obtained for K. lactis 90-3 and 90-4. A correlation between the ability to grow at higher temperature and the thermostability of the superoxide dismutase enzyme synthesized was observed. A comparison of the operational stability of the superoxide dismutase of all tested strains suggests that the enzyme of K. lactis strains was more thermostable than that of the other tested microorganisms. 相似文献
7.
Band 3 protein extracted from human erythrocyte membranes by Triton X-100 was recombined with the major classes of phospholipid occurring in the erythrocyte membrane. The resulting vesicle systems were characterized with respect to recoveries, phospholipid composition, protein content and vesicle size as well as capacity and activation energy of sulfate transport. Transport was classified into band-3-specific fluxes and unspecific permeability by inhibitors. Transport numbers (sulfate ions per band 3 per minute) served as a measure of functional recovery after reconstitution. The transport properties of band 3 proved to be insensitive to replacement of phosphatidylcholine by phosphatidylethanolamine, while sphingomyelin and phosphatidylserine gradually inactivated band-3-specific anion transport when present at mole fractions exceeding 30 mol%. The activation energy of transport remained unaltered in spite of the decrease in transport numbers. The results, which are discussed in terms of requirements of band 3 protein function with respect to the fluidity and surface charge of its lipid environment, provide a new piece of evidence that the transport function of band 3 protein depends on the properties of its lipid environment just as the catalytic properties of some other membrane enzymes. The well-established species differences in anion transport (Gruber, W. and Deuticke, B. (1973) J. Membrane Biol. 13, 19–36) may to some extent reflect this lipid dependence. 相似文献
8.
Scavenging of superoxide radical by ascorbic acid 总被引:1,自引:0,他引:1
Using acetaldehyde and xanthine oxidase as the source of suPeroxide radical, the second order rate constant for the reaction
between ascorbic acid and superoxide radical was estimated to be 8.2 X 107 M-1 s-1. In rats, the average tissue concentration of ascorbic acid was of the order of 10-3 M and that of superoxide dismutase was of the order of 10-6 M. So, taking together both the rate constants and the tissue concentrations, the efficacy of ascorbic acid for scavenging
superoxide radical in animal tissues appears to be better than that of suPeroxide dismutase. The significance of ascorbic
acid as a scavenger of superoxide radical has been discussed from the point of view of the evolution of ascorbic acid synthesizing
capacity of terrestrial vertebrates. 相似文献
9.
Ivan Tayarani Jean Chaudiere Jeanne-Marie Lefauconnier Jean-Marie Bourre 《Journal of neurochemistry》1987,48(5):1399-1402
The content of polyunsaturated fatty acids, the activities of superoxide dismutase (SOD), glutathione peroxidase, glutathione reductase, and catalase, and the concentration of reduced glutathione were measured in cerebral microvessels isolated from rat brain. Polyunsaturated fatty acids, mainly arachidonic, linoleic, and docosahexaenoic acids, accounted for 32% of total fatty acids in cerebral microvessels. Whereas total SOD activity in the microvessels was slightly lower than that found in cerebrum and cerebellum, glutathione peroxidase and glutathione reductase activities were twice as high and catalase activity was four times higher. Glutathione peroxidase in microvessels is active on both hydrogen peroxide and cumen hydroperoxide, and it is strongly inhibited by mercaptosuccinate. After several hours of preparation, the concentration of reduced glutathione in isolated microvessels was 0.7 mumol/mg of protein, which corresponds to a concentration of approximately 3.5 mM. Our results indicate that the blood-brain barrier contains large amounts of peroxide-detoxifying enzymes, which may act, in vivo, to protect its highly polyunsaturated membranes against oxidative alterations. 相似文献
10.
Mass spectrometric determinations of O2 affinities by the rumen fungus Neocallimastix patriciarum indicated a stable respiration under liquid phase O2 concentrations up to 10 M, the apparent K
m for O2 under these conditions was 4.0 M. Exposure to O2 concentrations in excess of 10 M resulted in rapid inactivation of the observed respiration. Calculated H2 evolution rates for the organism are 8.1 nmol min-1 per mg of protein. Exposure to liquid-phase O2 concentrations in excess of 1.4 M caused 50% inhibition of H2 production. That superoxide and peroxide are amongst the products of respiration was shown by the use of ESR spectroscopy with the spin trapping agent 5,5-dimethyl-l-pyrroline-N-oxide. An active superoxide dismutase was present, but catalase could not be detected.Abbreviations ESR
electron spin resonance
- DMPO
5,5-dimethyl-l-pyrroline-N-oxide
- DETAPAC
diethylene-triamine pentaacetic acid 相似文献