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42.
Yu Wang Huimin Xu Laura L. Grochowski Robert H. White 《Journal of bacteriology》2014,196(17):3191-3198
The gene encoding 7,8-dihydroneopterin aldolase (DHNA) was recently identified in archaea through comparative genomics as being involved in methanopterin biosynthesis (V. Crécy-Lagard, G. Phillips, L. L. Grochowski, B. El Yacoubi, F. Jenney, M. W. Adams, A. G. Murzin, and R. H. White, ACS Chem. Biol. 7:1807–1816, 2012, doi:10.1021/cb300342u). Archaeal DHNA shows a unique secondary and quaternary structure compared with bacterial and plant DHNAs. Here, we report a detailed biochemical examination of DHNA from the methanogen Methanocaldococcus jannaschii. Kinetic studies show that M. jannaschii DHNA possesses a catalytic capability with a kcat/Km above 105 M−1 s−1 at 70°C, and at room temperature it exhibits a turnover number (0.07 s−1) comparable to bacterial DHNAs. We also found that this enzyme follows an acid-base catalytic mechanism similar to the bacterial DHNAs, except when using alternative catalytic residues. We propose that in the absence of lysine, which is considered to be the general base in bacterial DHNAs, an invariant water molecule likely functions as the catalytic base, and the strictly conserved His35 and Gln61 residues serve as the hydrogen bond partners to adjust the basicity of the water molecule. Indeed, substitution of either His35 or Gln61 causes a 20-fold decrease in kcat. An invariant Tyr78 is also shown to be important for catalysis, likely functioning as a general acid. Glu25 plays an important role in substrate binding, since replacing Glu25 by Gln caused a ≥25-fold increase in Km. These results provide important insights into the catalytic mechanism of archaeal DHNAs. 相似文献
43.
Anna Wojakowska Dorota Muth Dorota Narożna Cezary Mądrzak Maciej Stobiecki Piotr Kachlicki 《Metabolomics : Official journal of the Metabolomic Society》2013,9(3):575-589
Plant interactions with environmental factors cause changes in the metabolism and regulation of biochemical and physiological processes. Plant defense against pathogenic microorganisms depends on an innate immunity system that is activated as a result of infection. There are two mechanisms of triggering this system: basal immunity activated as a result of a perception of microbe-associated molecular patterns through pattern recognition receptors situated on the cell surface and effector-triggered immunity (ETI). An induced biosynthesis of bioactive secondary metabolites, in particular phytoalexins, is one of the mechanisms of plant defense to fungal infection. Results of the study on narrow leaf lupin (Lupinus angustifolius L.) plants infected with the anthracnose fungus Colletotrichum lupini and treated with fungal phytotoxic metabolites are described in the paper. The C. lupini phytotoxins were isolated from liquid cultures, purified and partially characterized with physicochemical methods. Accumulation of secondary metabolites on leaf surface and within the tissues of plants either infected, treated with the fungal phytotoxin or submitted to both treatments was studied using GC-MS and LC-MS, respectively. Substantial differences in isoflavone aglycones and glycoconjugate profiles occurred in response to different ways of plant treatment. 相似文献
44.
Paczkowski C Musial A Wlodkowski L Kalinowska M Wojciechowski ZA 《Biotechnology letters》2007,29(9):1403-1408
The regioselective acylation of cholesteryl β-d-glucoside, at the C-6 of the glucose moiety, was achieved using microbial lipases in organic solvents. With palmitic acid
as an acyl donor 81 or 63% conversions of cholesteryl glucoside to its 6′-O-palmitoyl derivative were obtained using Candida antarctica or Rhizomucor miehei enzymes, respectively. High yields (64–92%) were also obtained with fatty acids 6:0–22:0 and 16:1 (n-7). The synthesis of
cholesteryl (6′-O-palmitoyl)glucoside was also achieved via transesterification, using mono-, di- and tri-palmitoylglycerols or methyl and ethyl palmitate as acyl sources. With R. miehei lipase transesterification between methyl palmitate (80 mM) and cholesteryl glucoside (1 mM) proceeded after 24 h with a
nearly quantitative yield (97%). 相似文献
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Zinc and cadmium analysis in human prostate neoplasms 总被引:4,自引:0,他引:4
Magdalena Brys Agnieszka D. Nawrocka Eügeniüsz MlekoŚ Cezary Zydek Marek Foksinski Andrzej Barecki Wanda M. Krajewska 《Biological trace element research》1997,59(1-3):145-152
The objective of this study was to test the hypothesis that prostatic cancer is associated with the changes of zinc (Zn) and
cadmium (Cd) concentration. Normal prostate, benign prostatic hyperplasia (BPH), and prostatic carcinoma (PCA) were analyzed
for Zn and Cd by atomic absorption spectrometry. Cd level was measured using a graphite furnace and Zn level was measured
by flame mode. Metal content was assessed in whole tissues and in nuclear, plasma membrane, and cytosolic fractions. An increase
of Zn content in BPH, but a decrease in PCA as compared to normal tissue, was observed. Cd concentration appeared to be higher
in BPH and PCA than in normal tissue. No correlation between Zn and Cd level was found in BPH specimens obtained from the
same patients. Probability values ofp ≤0.05 were considered to indicate significant differences. Obtained results seem to support the hypothesis of Cd carcinogenicity
and preventing function of Zn in prostatic cancer. Plasma membrane fraction corresponding to lysosomal, mitochondrial, and
microsomal subcellular compartments are probably critical in Zn and Cd participation in human prostate neoplasms. 相似文献
48.
Cezary Wójcik Kimberly Lohe Chenzhong Kuang Yan Xiao Zeida Jouni Eduard Poels 《Journal of cellular and molecular medicine》2014,18(4):590-599
We have evaluated the effects of three different omega‐3 polyunsaturated fatty acids (ω‐3 PUFAs) – docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA) on fat accumulation and expression of adipogenic and inflammatory markers using both 3T3‐L1 pre‐adipocytes and differentiated 3T3‐L1 adipocytes. Our results indicate that ω‐3 PUFAs induce the degradation of fatty acid synthase through the ubiquitin‐proteasome system, which is likely to have beneficial metabolic effect on adipose cells. Omega‐3 PUFAs also increase overall levels of polyubiquitinated proteins, at least in part through decreasing the expression of proteasome subunits. Moreover, adipocytes are resistant to proteasome inhibition, which induces adipophilin while decreasing perilipin expression. On the other hand, ω‐3 PUFAs decrease expression of SREBP1 while inducing expression of adipophilin and GLUT4. Moreover, all three ω‐3 PUFAs appear to induce tumour necrosis factor‐α without affecting NFκB levels. All three ω‐3 PUFAs appear to have overall similar effects. Further research is needed to elucidate their mechanism of action. 相似文献
49.
J. Eduardo Fajardo Rojan Shrestha Nelson Gil Adam Belsom Silvia N. Crivelli Cezary Czaplewski Krzysztof Fidelis Sergei Grudinin Mikhail Karasikov Agnieszka S. Karczyńska Andriy Kryshtafovych Alexander Leitner Adam Liwo Emilia A. Lubecka Bohdan Monastyrskyy Guillaume Pagès Juri Rappsilber Adam K. Sieradzan Celina Sikorska Esben Trabjerg Andras Fiser 《Proteins》2019,87(12):1283-1297
With the advance of experimental procedures obtaining chemical crosslinking information is becoming a fast and routine practice. Information on crosslinks can greatly enhance the accuracy of protein structure modeling. Here, we review the current state of the art in modeling protein structures with the assistance of experimentally determined chemical crosslinks within the framework of the 13th meeting of Critical Assessment of Structure Prediction approaches. This largest-to-date blind assessment reveals benefits of using data assistance in difficult to model protein structure prediction cases. However, in a broader context, it also suggests that with the unprecedented advance in accuracy to predict contacts in recent years, experimental crosslinks will be useful only if their specificity and accuracy further improved and they are better integrated into computational workflows. 相似文献
50.
Regulation of apoptosis by the ubiquitin and proteasome pathway 总被引:5,自引:1,他引:5
Wójcik C 《Journal of cellular and molecular medicine》2002,6(1):25-48
Regulated proteolysis plays important roles in cell physiology as well as in pathological conditions. In most of the cases, regulated proteolysis is carried out by the ubiquitin- and proteasome-dependent proteolytic system, which is also in charge of the bulk of cytoplasmic proteolysis. However, apoptosis or the process of programmed cell death is regulated by a different proteolytic system, i.e . by caspases, a family of specialized cysteine proteases. Nevertheless, there is plenty of evidence of a crosstalk between the apoptotic pathways and the ubiquitin and proteasome system, whose function in apoptosis appears to be very complex. Proteasome inhibitors induce apoptosis in multiple cell types, while in other they are relatively harmless or even prevent apoptosis induced by other stimuli. Proteasomes degrade specific proteins during apoptosis, but on the other hand some components of the proteasome system are degraded by caspases. The knowledge about the involvement of the ubiquitin- and proteasome-dependent system in apoptosis is already clinically exploited, since proteasome inhibitors are being tested as experimental drugs in the treatment of cancer and other pathological conditions, where manipulation of apoptosis is desirable. 相似文献