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51.
5-Lipoxygenase: regulation of expression and enzyme activity 总被引:8,自引:0,他引:8
5-Lipoxygenase (5-LO) catalyzes the first two steps in the biosynthesis of leukotrienes, a group of pro-inflammatory lipid mediators derived from arachidonic acid. Leukotriene antagonists are used in the treatment of asthma, and the potential role of leukotrienes in atherosclerosis, another chronic inflammatory disease, has recently received considerable attention. In addition, some possible effects of 5-LO metabolites in tumorigenesis have emerged. Thus, knowledge of the biochemistry of this enzyme has potential implications for the treatment of various diseases. Recent advances have expanded our understanding of the regulatory mechanisms underlying the expression and control of 5-LO activity. With regard to the control of enzyme activity, many of these findings focus on the N-terminal domain of 5-LO. 相似文献
52.
In an attempt to improve our abilities to predict peroxisomal proteins, we have combined machine-learning techniques for analyzing peroxisomal targeting signals (PTS1) with domain-based cross-species comparisons between eight eukaryotic genomes. Our results indicate that this combined approach has a significantly higher specificity than earlier attempts to predict peroxisomal localization, without a loss in sensitivity. This allowed us to predict 430 peroxisomal proteins that almost completely lack a localization annotation. These proteins can be grouped into 29 families covering most of the known steps in all known peroxisomal pathways. In general, plants have the highest number of predicted peroxisomal proteins, and fungi the smallest number. 相似文献
53.
Characterization of O-acetyl-(4-O-methylglucurono)xylan isolated from birch and beech 总被引:6,自引:0,他引:6
The structures of water-soluble birch and beech xylans, extracted from holocellulose using dimethyl sulfoxide, were determined employing 1H and 13C NMR spectroscopy together with chemical analysis. These polysaccharides were found to be O-acetyl-(4-O-methylglucurono)xylans containing one 4-O-methylglucuronic acid substituent for approximately every 15 D-xylose residues. The average degree of acetylation of the xylose residues in these polymers was 0.4. The presence of the structural element -->4)[4-O-Me-alpha-D-GlcpA-(1-->2)][3-O-Ac]-beta-D-Xylp-(1--> was demonstrated. Additional acetyl groups were present as substituents at C-2 and/or C-3 of the xylopyranosyl residues. Utilizing size-exclusion chromatography in combination with mass spectroscopy, the weight-average molar masses (and polydispersities) were shown to be 8000 (1.09) and 11,100 (1.08) for birch and beech xylan, respectively. 相似文献
54.
55.
Emanuelsson O 《Briefings in bioinformatics》2002,3(4):361-376
Predicting the subcellular localisation of proteins is an important part of the elucidation of their functions and interactions. Here, the amino acid sequence motifs that direct proteins to their proper subcellular compartment are surveyed, different methods for localisation prediction are discussed, and some benchmarks for the more commonly used predictors are presented. 相似文献
56.
Kristian Björnstad Olof Beck Anders Helander 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2009,877(11-12):1162-1168
A sensitive and specific LC–MS/MS method for simultaneous detection of 10 plant-derived psychoactive substances (atropine, N,N-dimethyltryptamine, ephedrine, harmaline, harmine, ibogaine, lysergic acid amide, psilocin, scopolamine and yohimbine) in urine was developed. Direct injection of urine diluted with 3 deuterated internal standards allowed for a readily accessible method suitable for application in clinical intoxication cases. Separation was achieved using reversed phase chromatography and gradient elution with a total analysis time of 14 min. Electrospray ionization was used and ions were monitored in the positive selected reaction monitoring mode. The calibration curves were linear (r2 > 0.999) and the total imprecision at high (1000 μg/L) and low (50 μg/L) substance concentrations were 4.9–13.8% and 8.3–26%, respectively. Infusing the analytes post column and injecting matrix samples showed limited influence by ion suppression. The multi-component method proved to be useful for investigation of authentic cases of intoxication with plant-derived psychoactive drugs and was indicated to cover the clinically relevant concentration ranges. 相似文献
57.
Purification to apparent homogeneity of a thymocyte specific growth factor from calf thymus 总被引:1,自引:0,他引:1
A thymic peptide previously found to recruit thymocytes from G1 into S phase has been purified from a crude thymic extract by subsequent steps of gel exclusion chromatography and reverse phase high performance liquid chromatography (HPLC). The purified material, which appeared homogeneous on thin-layer chromatography and HPLC, stimulated the DNA synthesis of cultured guinea pig thymocytes in a nanomolar concentration range. The amino acid composition revealed a high content of acidic amino acids and no apparent homology to previously defined growth factors and thymus differentiation hormones. 相似文献
58.
Four coumarins and seven isoprenoid compounds have been identified in potato tubers infected with Phoma exigua var. foveata. Among these were the 7-O-β-D-glucopyranoside of 7-hydroxy-6,8-dimethoxycoumarin (isofraxidin) and the sesquiterpene 2-(11,12-dihydroxy-11-methylethyl)-6,10-dimethyl-spiro[4,5]dec-6-en-8-one and its 12-O-β-D-glucopyranoside, which apparently have not been previously identified in potato tubers. At least two diastereoisomers of the latter glucoside were present. Analysis of eight fluorescent compounds in different parts of infected potatoes was performed by an improved HPLC technique. 相似文献
59.
60.
Arachidonic acid promotes phosphorylation of 5-lipoxygenase at Ser-271 by MAPK-activated protein kinase 2 (MK2) 总被引:3,自引:0,他引:3
Werz O Szellas D Steinhilber D Rådmark O 《The Journal of biological chemistry》2002,277(17):14793-14800
We demonstrated previously that 5-lipoxygenase (5-LO), a key enzyme in leukotriene biosynthesis, can be phosphorylated by p38 MAPK-regulated MAPKAP kinases (MKs). Here we show that mutation of Ser-271 to Ala in 5-LO abolished MK2 catalyzed phosphorylation and clearly reduced phosphorylation by kinases prepared from stimulated polymorphonuclear leukocytes and Mono Mac 6 cells. Compared with heat shock protein 27 (Hsp-27), 5-LO was a weak substrate for MK2. However, the addition of unsaturated fatty acids (i.e. arachidonate 1-50 microm) up-regulated phosphorylation of 5-LO, but not of Hsp-27, by active MK2 in vitro, resulting in a similar phosphorylation as for Hsp-27. 5-LO was phosphorylated also by other serine/threonine kinases recognizing the motif Arg-Xaa-Xaa-Ser (protein kinase A, Ca(2+)/calmodulin-dependent kinase II), but these activities were not increased by fatty acids. HeLa cells expressing wild type 5-LO or S271A-5-LO, showed prominent 5-LO activity when incubated with Ca(2+)-ionophore plus arachidonate. However, when stimulated with only exogenous arachidonic acid, activity for the S271A mutant was significantly lower as compared with wild type 5-LO. It appears that phosphorylation at Ser-271 is more important for 5-LO activity induced by a stimulus that does not prominently increase intracellular Ca(2+) and that arachidonic acid stimulates leukotriene biosynthesis also by promoting this MK2-catalyzed phosphorylation. 相似文献