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1.
Ascorbic acid, or vitamin C, can recycle -tocopherol in lipid bilayers, but even sparing of -tocopherol has not been a consistent finding in intact cells. Therefore, we tested the ability of ascorbate loading to spare -tocopherol and to prevent lipid peroxidation of cultured H4IIE rat liver cells. Although -tocopherol was undetectable in H4IIE cells, its cell content was increased by overnight incubation with -tocopherol in culture. Cells incubated with ascorbate 2-phosphate accumulated ascorbate to concentrations as high as 0.6 mM after overnight loading, but also released ascorbate into the medium. Ascorbate loading of -tocopherol-treated cells spared -tocopherol in a concentration-dependent manner during overnight incubation. Lipid peroxidative damage, measured as a decrease in fluorescence of cell-bound cis-parinaric acid, was decreased in cells loaded with either -tocopherol or ascorbate 2-phosphate, and showed an additive effect. These results suggest that ascorbate loading of H4IIE cells spares cellular -tocopherol and either directly or through recycling of -tocopherol prevents lipid peroxidative damage due to oxidant stress in culture. 相似文献
2.
W. Bockelmann V. Monnet A. Geis M. Teuber J. C. Gripon 《Applied microbiology and biotechnology》1989,31(3):278-282
Summary Cell wall-associated proteinases were isolated from Lactococcus lactis subsp. cremoris AC1 and subsp. lactis NCDO 763 in order to compare their specificities towards different caseins. Two purification strategies were applied. Cells grown in casein-free M17 medium were a suitable starting material for purification, since electrophoretic purity could be achieved after one chromatographic step. Both enzymes has an apparent molecular mass of about 145000 daltons as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Electrophoresis and reversed phase HPLC patterns of hydrolysates of s1-, s2-, -, and K-caseins indicated that both proteinases had a similar specificity. The enzyme of L. lactis subsp. lactis split s1- and s2-caseins more extensively than that of L. lactis subsp. cremoris. 相似文献
3.
The effect of-tocopherol (T) on partitioning and fluidity changes occurring in phospholipid liposomes have been investigated by monitoring the X-band ESR spectrum of the high resolution amphiphilic spin probe perdeutero-di-t-butyl nitroxide (PDDTBN), which partitions in the lipid and water phase of liposomes, showing all the three resonances from each phase well resolved. 相似文献
4.
Summary A study of the molar ratio dependence of the incorporation of -tocopherol into single-lamellar vesicles showed that the number of molecules which the bilayers can accommodate increased linearly with increasing -tocopherol/phosphatidylcholine initial molar ratios till about 0.05, then approached a saturation limit. At 5 mol%, one -tocopherol molecule per 60 phospholipids can be incorporated into the membranes. Up to this limit the distribution of -tocopherol in the bilayers is uniform, while at initial molar ratios higher than 0.05 a disproportionation toward the inner monolayer of the vesicles is observed. The average outer/total ratio is found to be 0.27±0.03 at -tocopherol/phosphatidylcholine molar ratios above 0.07 and is similar to asymmetrical distributions that have been reported in vesicles containing other one-chain amphiphiles (e.g., cholesterol). This large disproportionation is in contrast with the packing distribution of certain twochain amphiphiles, and indicates that one of the driving forces for asymmetry formation in lipid bilayers might be dependent on the number of hydrocarbon chains per amphiphile molecule. A possible reason for the disproportionation effect observed in our experiments is the displacement of unsaturated phospholipids to the outer monolayer of the single-lamellar vesicles, by the more rigid isoprene units of -tocopherol. 相似文献
5.
James R. Litton Jr 《Hydrobiologia》1987,147(1):135-139
Experiments were undertaken to determine molecular specificity of Vitamin E-effects on lifespan and fecundity in four bdelloid rotifers (Habrotrocha sp., Philodina sp., Pleuretra sp., and Rotaria sp.). Results indicate that lifespan and fecundity could be significantly increased by addition of any one of three tocopherol compounds (d--, -, and -tocopherol) to the rotifer medium. Life table functions were increased the most by the d--tocopherol form. Improvement of these life table functions was not achieved by substitution of tocopherol analogs or other antioxidants in the rotifer medium. 相似文献
6.
Much controversy exists as to the level at which light exerts control over the biosynthesis of the photosynthetic apparatus in higher plants and other organisms. The eukaryotic red algaCyanidium caldarium, like higher plants, undergoes light induction of chlorophyll synthesis. In addition to chlorophyll the alga also synthesises the linear tetrapyrrole phycocyanobilin, which is combined with or apobiliproteins to form phycocyanin, the major light-harvesting pigment in this organism. We have previously shown that the tetrapyrrole precursor 5-aminolaevulinic acid (ALA) can substitute for light in inducing the biosynthesis of the phycocyanobilin moiety of this protein. We have also described the appearance of a protein of similar isoelectric point and molecular weight to phycocyanin in ALA-fed cells (Turner et al., 1992, Plant Physiol Biochem 30: 309–314). We now report on the protein's immunological and sequence identity with phycocyanin and subunits, and provide further evidence that bilin-apoprotein ligation is light dependent. 相似文献
7.
Isoelectrofocusing, product analysis, thermal denaturation studies and affinity chromatography on cycloheptaamylose-Sephadex were used to identify the amylolytic enzymes in internodes of deepwater rice (Oryza sativa L.). Amylolytic activity in internodes of deepwater rice consists of -amylase (sometimes separated into two isoforms) and of -amylase. During submergence of whole plants, -amylase activity increases in young, growing internodes, but -amylase activity declines. Although non-growing, mature internodes contain higher levels of -amylase than do the elongating younger internodes, the effect of submergence on amylase activities in both tissues follows the same trend. Submergence, gibberellic acid (GA3) and ethylene all promote -amylase activity in growing and non-growing internodes of excised deepwater-rice stem sections. Inhibitor studies showed that submergence and ethylene promote -amylase activity in the absence of endogenous gibberellin (GA), and GA3 enhances -amylase activity when ethylene action is inhibited. Therefore, ethylene and GA appear to increase -amylase activity independently of each other. Enhanced -amylase activities are probably responsible for the mobilization of carbohydrates which are needed to support internode elongation during submergence of deepwater rice.Abbreviations CHA
cycloheptaamylose
- GA3
gibberellic acid
- NBD
2,5-norbornadiene
- TCY
tetcyclacis 相似文献
8.
Summary -Tocopherol was identified in lipid extracts of bovine retinal outer segment (ROS) preparations. Positive identification was obtained by the thin layer chromatographic characteristics of the tocopherol form and its oxidation product -tocopherylquinone, and by the ultraviolet spectrum of the oxidized and KBH4-reduced form of the tocopherylquinone. In the ROS preparations used, -tocopherol chromanol was the predominant species, the quinone form accounting for 25% or less of the total. The concentration of -tocopherol in the ROS preparations was about 0.1 mole -tocopherol per mole rhodopsin, or about 1 nmole/mg, protein. Mitochondria from bovine retina contained about 0.4 nmole -tocopherol per mg protein. 相似文献
9.
The percentages of the -chain variant Hb G-Philadelphia (Hb G) or 2 68 AsnLys2 were evaluated in 84 adult and 18 newborn heterozygotes. These included members of three families who were studied in more detail by nucleic acid hybridization techniques. The adult heterozygotes fell in two categories, one with a higher proportion of Hb G [46.5±1.0% (SD), N=21] and another with lower values (33.9±3.4%, N=63). Among the newborn heterozygotes, two babies fell in the category with the higher proportion of Hb G while 16 babies gave values between 25 and 34%. Studies of -chain gene organization on the parents of one neonate with a Hb G level of 27% at birth and 37% at 8 months excluded the presence of chromosomes with triplicated -chain genes which could lead to the 0G/ genotype. Rather, these studies on five Hb G heterozygotes from three families confirmed the linkage between Hb G and a specific type of -thalassemia-2 associated with the presence of a 16-kbp Bgl II fragment which most probably carries the G locus since it has been found in 19 Hb G heterozygotes studied to date. The presence of an -thal-2 heterozygosity and three -chain genes (0G/) was confirmed among Hb G heterozygotes with lower proportions of this variant. It is likely that the even lower values found in some newborn could arise through defective assembly of G- dimers. The presence of an -thal-2 homozygosity and two active -chain genes, one on each chromosome (0G/0), was confirmed among heterozygotes with the higher proportion of Hb G. One of each of these categories was present in each of the three families investigated. This type of variability in the number of active -chain genes due to a heterozygosity or a homozygosity for -thalassemia-2 explains the trimodality of Hb S percentages among heterozygotes and the atypical hematological or biosynthetic features among patients with -thalassemia and sickle-cell syndromes.This research was supported by USPHS Research Grants HLB-05168 and HLB-15158 and by designated research funds of the Veterans Administration. This is Contribution No. 0693 of the Department of Cell and Molecular Biology, Medical College of Georgia, Augusta. 相似文献
10.
Fabio Dall'Olio 《Glycoconjugate journal》2000,17(10):669-676
Sialylation represents one of the most frequently occurring terminations of the oligosaccharide chains of glycoproteins and glycolipids. Sialic acid is commonly found ,3- or ,6-linked to galactose (Gal), ,6-linked to N-acetylgalactosamine (GalNAc) or ,8-linked to another sialic acid. The biosynthesis of the various linkages is mediated by the different members of the sialyltransferase family. The addition of sialic acid in ,6-linkage to the galactose residue of lactosamine (type 2 chains) is catalyzed by -galactoside ,6-sialyltransferase (ST6Gal.I). Although expressed by a single gene, this enzyme shows a complex pattern of regulation which allows its tissue- and stage-specific modulation. The cognate oligosaccharide structure, NeuAc,6Gal1,4GIcNAc, is widely distributed among tissues and is involved in biological processes such as the regulation of the immune response and the progression of colon cancer. This review summarizes the current knowledge on the biochemistry of ST6Gal.I and on the functional role of the sialyl-,6-lactosaminyl structure. 相似文献
11.
Hirotaka Yamamoto Yoichi Kaneko David Vandermulen Donna Kersey Edward Mkrdichian Leonard Cerullo Jan Leestma Joseph R. Moskal 《Glycoconjugate journal》1995,12(6):848-856
The expression of CMP-NeuAc: Gal1,4GlcNAc 2,6 sialyltransferase (2,6-ST) [EC 2.4.99.1] and glycoproteins bearing 2,6-linked sialic acids were examined in primary human brain tumours and cell lines. 79% (19/24) of the meningiomas expressed 2,6-ST mRNA, 42% (10/24) of which showed very high expression. 2,6-ST mRNA expression was undetectable in normal brain tissue. In contrast, only 1/13 of the gliomas examined expressed detectable 2,6-ST mRNA. Metastases to the brain did not express measurable amounts of 2,6-ST mRNA. Less expression was found in malignant (i.e., anaplastic) compared to benign (i.e. meningothelial) meningiomas. Two-dimensional SDS-PAGE of glioma and meningioma proteins, followed bySambucus nigra lectin staining, revealed the presence of a glycoprotein bearing 2,6-linked sialic acids,M
r=53 kDa and a pI=7.0 (MEN-1) that appeared in all seven of the meningiomas examined, but was expressed at barely detectable levels, if at all, in seven out of the seven glioblastomas examined. Thus, decreased 2,6-ST expression may play a role in the aggressive nature of anaplastic meningiomas, but appears to be virtually absent in all tumours of glial origin. 相似文献
12.
L. M. P. de Moraes S. Astolfi-filho S. G. Oliver 《Applied microbiology and biotechnology》1995,43(6):1067-1076
Eight constructions involving the Bacillus subtilis -amylase gene (amyE), a mouse pancreatic -amylase cDNA (AMY2) and an Aspergillus awamori glucoamylase cDNA (glaA) were prepared: three fusion genes, involving one -amylase and the glucoamylase, two double-cassette plasmids (expressing one or other -amylase and the glucoamylase) and three single-cassette plasmids, expressing the individual coding sequences. Following transformation of each plasmid into Saccharomyces cerevisiae, a plate test revealed that the largest starch hydrolysis halo was produced by the strain bearing the B. subtilis -amylase/glucoamylase fusion (BsAAase/GAase), and the smallest halo by the one expressing the mouse pancreatic -amylase/glucoamylase fusion (MAAase/GAase). When assayed for enzymatic activity in liquid medium, the strains bearing the fusion and the double-cassette plasmids involving B. subtilis -amylase and the glucoamylase exhibited both enzymic activities. Moreover, the BsAAase/GAase hybrid was able to adsorb and digest raw starch. The MAAse/GAase fusion protein was found to exhibit only -amylase activity. Finally, the capacity to grow on soluble and corn starch was tested in liquid medium for the strains bearing plasmids coding for the fusion proteins and the separate enzymes. The strain carrying the double-cassette BsAAase + GAase, which produced one of the smallest hydrolysis haloes in the place test, showed the best performance, not only in digesting soluble and corn starch but also in using all of the hydrolysis products for growth. The transformant bearing the BsAAase/GAase fusion was able to grow on soluble starch, but not on corn starch. 相似文献
13.
Soo-Jin Cho Seong Joo Park Jong-Soon Lim Young Hah Rhee Kwang-Soo Shin 《Biotechnology letters》2002,24(16):1337-1340
The oxidation of five polycyclic aromatic hydrocarbons; anthracene, benzo()pyrene, fluoranthene, phenanthrene and pyrene was catalyzed by laccase from Coriolus hirsutus in the presence of the redox mediators, 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) and 1-hydroxybenzotriazole (HBT). In the ABTS-mediated system, benzo()pyrene was the most rapidly oxidized substrate, with anthracene being the most rapidly oxidized in the HBT-mediated system. There was no clear relationship between the ionization potential and the oxidation of the substrates. ABTS increased the oxidation of benzo()pyrene more than HBT but the oxidation of the other PAHs tested were the opposite. The mediators used in conjunction increased the oxidation of benzo()pyrene compared to using the mediators alone. 相似文献
14.
Masayuki Gotoh Jun-ichi Kitanaka Yoshimi Hirasawa Kaoru Kondo Akemichi Baba 《Neurochemical research》1994,19(6):679-685
Desensitization of prostaglandin (PG) F2 receptor-mediated phosphoinositide (PI) hydrolysis was investigated in cultured rat astrocytes. Prolonged exposure of astrocytes differentiated by dibutyryl cyclic AMP-treatment to PGF2 caused the desensitization of subsequent PGF2-induced PI hydrolysis. The desensitization was time- and PGF2 dose-dependent; maximal decrease in the PI hydrolysis was observed after exposure to 10 M PGF2 for 4 h and the degree of the desensitization was 31.7±2.7% of control. Pretreatment with either PGD2 or PGE2 also induced the desensitization of subsequent PGF2-stimulated PI hydrolysis and conversely pretreatment of PGF2 decreased the PI responses to PGD2 and PGE2. The desensitization prevented by phloretin and was reversible upon removal of the agonist. Protein synthesis inhibitors blocked the recovery of the desensitization. Treatment of the cells with phorbol 12-myristate 13-acetate had no effect on the desensitization. These results suggest that prolonged exposure of the astrocytes to PGF2 caused the desensitization of the receptors. 相似文献
15.
Summary Detailed restriction enzyme analysis of the DNA from a Chinese female showed that one of her chromosomes had a >17.5 kb deletion of DNA, including the , 2, and 1 globin genes, which is present in many Southeast Asians with an -thalassemia-1 chromosome. Her normal chromosome had the expected cluster of -like globin genes (5----2-1-3), but the segment of DNA between the two globin genes was elongated by some 0.5–0.7 kb. Analyses of various restriction sites suggested that this normal variant of the human globin gene complex is due to a crossover between a normal chromosome with () and a chromosome with an -thalassemia-2 (–3.7) and an -21-hybrid gene. 相似文献
16.
Seymour Zigman Thurma McDaniel Joanne B. Schultz John Reddan Mohsen Meydani 《Molecular and cellular biochemistry》1995,143(1):35-46
The purpose of this research is to observe the near-UV radiation induced damage to cultured rabbit and squirrel lens epithelial cells as related to destruction and alterations of specific biochemical targets in the cells and to determine protective effects on the cells and targets that are provided by -tocopherol.Confluent monolayers of cultured rabbit and squirrel lens epithelial cells were exposed to black light (BL) lamps, which emit predominantly UV-A radiation. These cells received a mixture 3 J/cm2 of UV-A and 4 mJ/cm2 of UV-B per h. This mixture is termed near UVA (ie:predominantly UV-A). Cells were exposed in Tyrode's or in MEM without or with -tocopherol added at 2.5–10 g/ml. Analyses of cell viability and survival, the physical state of cytoskeletal actin, and the activities of Na-K-ATPase and catalase were made.Exposure to near UVA damaged these cells as measured by vital staining and colony forming ability. Pretreatment with -tocopherol decreased the magnitude of near UVA cytotoxicity. Near UVA exposure in MEM always produced more damage to the cells and biochemical targets than in Tyrode's. Cytoskeletal actin was degraded and the activities of Na-K-ATPase and catalase were markedly inhibited by UV-exposure. All of these targets were at least partially protected by -tocopherol in the medium. Without -tocopherol added to the media, the viability and survival of the cells did not recover even after 25 h of incubation. Cell viability was better protected from near UVA by -tocopherol than was the ability to grow into colonies. This indicates that -tocopherol protects actin, catalase, and Na-K-ATPase from near UVA damage. 相似文献
17.
Bartel Sabine Karczewski Peter Krause Ernst-Georg 《Molecular and cellular biochemistry》1996,163(1):31-38
The postnatal alterations of the composition of a subunit isoforms (Gic, G i3 Go, and Gq of G proteins, the adenylyl cyclase activity as well as of cAMP-regulated phosphoproteins e.g. troponin and phospholamban were investigated in the ventricular tissue of 1, 7, 30 days old rats. Quantitative immunodetection revealed a 5.7-fold decrease in Gi3 at 30th postnatal day compared with the postnatal day 1 and up to 15-fold at 4 months. The amounts of Gq and G as well as the G subunits were found to be higher in the earlier life period compared to the adult. In contrast, the content of Gs was uneffected by the developmental state. Basal adenylyl cyclase activity (pmoles cAMP/min × mg protein) increased from 30.9 ± 5.0, 36.8 ± 5.0 to 63.9 ± 5.9 at 1st, 7th and 30th postnatal day, respectively. Isoprenaline (100 M) enhanced the activity of adenylyl cyclase from day 1, 7–30 from 46.2 ± 7.0, 79.1 ± 9.2 to 120.5 ± 7.2, respectively. The effects of forskolin and NaF on adenylyl cyclase activity was found to be not influenced within the first postnatal month. Furthermore, a developmentally controlled expression of cardiac troponin I was observed (6-fold from the first to the 28th postnatal day) whereas the level of phospholamban was found to be age-independent.In conclusion, there is an increase in the efficiency of the -adrenergic signal transfer mainly caused by a reduction of the inhibitiory G proteins and a dominance of the Gs-linked pathway in the postnatal rat heart. Furthermore the developmentally controlled expression of troponin I might be of functional importance in the cAMP-supported relaxation. Additionally, altered Gq, Go and G pattern of the developing rat ventricle may play a role in the observed change of -adrenerg-mediated heart contractility as well as in cardiac differentiation and growth processes. 相似文献
18.
Shcheglovitov A. K. Zhelay T. I. Kondratskii A. P. Naidenov V. G. Shuba Ya. M. 《Neurophysiology》2004,36(2):93-101
We analyzed the effects of nifedipine on a family of recombinant low-threshold Ca2+ channels functionally expressed in Xenopus oocytes and formed by three different subunits (1G, 1H, and 1I). The 1G and 1I channels demonstrated a low sensitivity to nifedipine even in high concentrations (IC50 = 98 and 243 M, maximum blocking intensity Amax = 25 and 47%, respectively). At the same time, the above agent effectively blocked channels formed by the 1H-subunit (IC50 = 5 M and Amax = 41%). The nifedipine-caused effects were voltage-dependent, and their changes depended on the initial state of the channel. In the case of 1G-subunits, the blockade was determined mostly by binding of nifedipine with closed channels, whereas in the cases of 1H- and 1I-subunits this resulted from binding of nifedipine with channels in the activated and inactivated states. The obtained data allow us to obtain estimates of the pharmacological properties of the above three subtypes of recombinant channels and, in the future, to compare these characteristics with the properties of low-threshold Ca2+ channels in native cells. 相似文献
19.
Gel-filtration-purified R-phycoerythrin and phycocyanin from the filamentous phase of Bangia atropurpurea were subjected to high performance anion exchange chromatographic separation. The purified R-phycoerythrin was a mixture of three charged-isomers that were well resolved in a Bio-Gel MA7P column by elution with a NaCl gradient in phosphate buffer. These were tentatively called phycoerythrin charged-isomers and were also separable from phycocyanin and allophycocyanin by the same system. Hence, it is suggested that the ion exchange chromatographic and the sample preparation methods presented in this report can be used to distinguish the various natures of biliproteins in red algae in addition to the polyacrylamide gel electrophoresis technique. Isomers of R-phycoerythrin have the same absorption and emission spectra and were studied for their subunit compositions by a PRP-3 reverse phase column chromatography. All three charged-isomers have the same and subunits in common but differ in their subunit. 相似文献
20.
The genes were cloned for the two apoprotein subunits, and ,of phycocyanin from the cyanobacterium Spirulina maxima = Arthrospiramaxima) strain F3. The - and -subunit gene-coding regionscontain 489 bp and 519 bp, respectively. The -subunit gene is upstreamfrom the -subunit gene, with a 111-bp segment separating them.Similarities between the -subunits of S. maxima and nine othercyanobacteria were between 58% and 99%, as were those between the -subunits. The maximum similarity between the - and -subunits from S. maxima was 27%. 相似文献