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排序方式: 共有148条查询结果,搜索用时 15 毫秒
31.
Lichtenthaler SF Dominguez DI Westmeyer GG Reiss K Haass C Saftig P De Strooper B Seed B 《The Journal of biological chemistry》2003,278(49):48713-48719
The aspartyl protease BACE1 cleaves the amyloid precursor protein and the sialyltransferase ST6Gal I and is important in the pathogenesis of Alzheimer's disease. The normal function of BACE1 and additional physiological substrates have not been identified. Here we show that BACE1 acts on the P-selectin glycoprotein ligand 1 (PSGL-1), which mediates leukocyte adhesion in inflammatory reactions. In human monocytic U937 and human embryonic kidney 293 cells expressing endogenous or transfected BACE1, PSGL-1 was cleaved by BACE1 to generate a soluble ectodomain and a C-terminal transmembrane fragment. No evidence of the cleavage fragment was seen in primary cells derived from mice deficient in BACE1. By using deletion constructs and enzymatic deglycosylation of the C-terminal PSGL-1 fragments, the cleavage site in PSGL-1 was mapped to the juxtamembrane region within the ectodomain. In an in vitro assay BACE1 catalyzed the formation of the PSGL-1 products seen in vivo. The cleavage occurred at a Leu-Ser peptide bond as identified by mass spectrometry using a synthetic peptide. We conclude that PSGL-1 is an additional substrate for BACE1. 相似文献
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33.
Incorporation and release of 14C-label in prenylquinones of Chlorella was investigated under steady state conditions. After one hour of 14CO2-photosynthesis all plastid quinones investigated were labeled. The highest label was found in phylloquinone (18%) while -tocopherol exhibits the lowest label (0.38%). Among the plastoquinones, plastohydroquinone-9 shows a higher labeling degree (5.1%) and a faster labeling kinetic than plastoquinone-9 (1.6%). After replacement of 14CO2 against 12CO2 the total radioactivity in plastohydroquinone-9, -tocopherol and phylloquinone decreases but in -tocoquinone and plastoquinone-9 proceeds further. From this labeling kinetic we conclude, that newly synthesized [14C]-tocopherol molecules are converted to [14C]-tocoquinone and [14C]plastohydroquinone-9 molecules to [14C]plastoquinone-9. From their 14C-incorporation kinetic half-lives could be calculated for all prenylquinones in the same ranges as previously found for the chlorophylls and carotenoids (Grumbach et al., 1978). Half-lives are shorter in plastohydroquinone-9 (30 min) and plastoquinone-9 (40 min) than in phylloquinone (55 min), -tocoquinone (50 min) and -tocopherol (220 min). This means that all prenyl-lipids such as chlorophyll a, -and -carotene, plastohydroquinone-9 and plastoquinone-9 which are more directly involved in the process of photosynthesis are subject to a continuous and higher turnover than the xanthophyll and -tocopherol. From the fast labeling kinetic and short half-lives of -tocoquinone and especially phylloquinone with a labeling degree of 12% after one hour of 14CO2 photosynthesis we suppose that perhaps these two prenylquinones are also involved in the photosynthetic activity of chloroplasts. 相似文献
34.
Abscisic acid (ABA) caused a 7–8-fold increase in volume flow in excised bean root systems and this was coupled with an increase in 42K, 36Cl and 24Na flux into the xylem. The transport of 42K and 36Cl increased by a factor larger than the stimulation of volume flow, resulting in an increase in the concentration of those ions in the xylem exudate. Carbonyclcyanide-m-chlorophenyl hydrazone, on the other hand, eliminated ABA-stimulated 42K transport and caused a further inhibition of 42K flux, thus providing additional support for the proposition that ABA stimulation may involve an energised process of ion transport. ABA also increased the accumulation of 24Na and 36Cl in bean root tissue, but not that of 42K. 相似文献
35.
Chlorophyll-protein levels and degree of thylakoid stacking in radish chloroplasts from high-light, low-light and bentazon-treated plants 总被引:3,自引:0,他引:3
Hartmut K. Lichtenthaler Gertrud Kuhn Ursula Prenzel Dieter Meier 《Physiologia plantarum》1982,56(2):183-188
Lemna gibba plants were incubated aseptically on medium containing labelled 10-7 M indole-3-acetic acid (IAA-1-14 C). Most of the radioactivity disappeared from the culture medium during a 24 h light period. A high percentage of the loss was due to photolysis and only a low percentage of the radioactivity was recovered in the plants. Uptake of 14 C by the plants was strongly stimulated by light. The radioactivity taken up by the plants was the sum of photosynthetically taken up 14 CO2 and 14 C taken up in IAA. Analyses with the indolo-α-pyrone fluorescence method revealed that the free IAA content was almost the same in plants grown in control and in IAA media for 5 h, whereas the amount of IAA which could be liberated by alkaline hydrolysis was doubled by the presence of IAA in the medium. 相似文献
36.
37.
Lichtenthaler HK 《Biochemical Society transactions》2000,28(6):785-789
The essential steps of the novel non-mevalonate pathway of isopentenyl diphosphate and isoprenoid biosynthesis in plants are described. The first five enzymes and genes of this 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol 4-phosphate (DOXP/MEP) pathway are known. The herbicide fosmidomycin specifically blocks the second enzyme, the DOXP reductoisomerase. The DOXP/MEP pathway is also present in several pathogenic bacteria and the malaria parasite. Hence, all herbicides and inhibitors blocking this novel isoprenoid pathway in plants are also potential drugs against malaria and diseases caused by pathogenic bacteria. 相似文献
38.
The volatile hemiterpene 2-methyl-3-buten-2-ol (MBO) is emitted from the needles of several pine species from the Western United States and contributes to ozone formation in the atmosphere. It is synthesised enzymatically from dimethylallyl diphosphate (DMAPP). We show here that needles of Pinus ponderosa Laws. incorporated [1-2H1]-1-deoxy-D-xylulose (d-DOX) into the emitted MBO, but not D,L-[2-13C]mevalonic acid lactone. Furthermore, MBO emission was inhibited by fosmidomycin, a specific inhibitor of the second enzyme of the mevalonate-independent pathway of isopentenyl diphosphate and DMAPP formation, i.e. the 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol 4-phosphate (DOXP/MEP) pathway. We thus prove that MBO emitted from needles of P. ponderosa is primarily formed via the DOXP/MEP pathway. 相似文献
39.
With a flash-lamp chlorophyll (Chl) fluorescence imaging system (FL-FIS) the photosynthetic activity of several thousand image points of intact shade and sun leaves of beech were screened in a non-destructive way within a few seconds. The photosynthetic activity was determined via imaging the Chl fluorescence at maximum Fp and steady state fluorescence Fs of the induction kinetics (Kautsky effect) and by a subsequent determination of the images of the fluorescence decrease ratio RFd and the ratio Fp/Fs. Both fluorescence ratios are linearly correlated to the photosynthetic CO2 fixation rates. This imaging method permitted to detect the gradients in photosynthetic capacity and the patchiness of photosynthetic quantum conversion across the leaf. Sun leaves of beech showed a higher photosynthetic capacity and differential pigment ratios (Chl a/b and Chls/carotenoids) than shade leaves. Profile analysis and histogram of the Chl fluorescence yield and the Chl fluorescence ratios allow to quantify the differences in photosynthetic activity between different leaf parts and between sun and shade leaves with a high statistical significance. 相似文献
40.
Anne Kathrin Müller-Rischart Anna Pilsl Patrick Beaudette Maria Patra Kamyar Hadian Maria Funke Regina Peis Alexandra Deinlein Carolin Schweimer Peer-Hendrik Kuhn Stefan F. Lichtenthaler Elisa Motori Silvana Hrelia Wolfgang Wurst Dietrich Trümbach Thomas Langer Daniel Krappmann Gunnar Dittmar Konstanze F. Winklhofer 《Molecular cell》2013,49(5):908-921
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