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Leukotrienes (LTs) are inflammatory mediators that play a pivotal role in many diseases like asthma bronchiale, atherosclerosis and in various types of cancer. The key enzyme for generation of LTs is the 5-lipoxygenase (5-LO). Here, we present a novel putative protein isoform of human 5-LO that lacks exon 4, termed 5-LOΔ4, identified in cells of lymphoid origin, namely the Burkitt lymphoma cell lines Raji and BL41 as well as primary B and T cells. Deletion of exon 4 does not shift the reading frame and therefore the mRNA is not subjected to non-mediated mRNA decay (NMD). By eliminating exon 4, the amino acids Trp144 until Ala184 are omitted in the corresponding protein. Transfection of HEK293T cells with a 5-LOΔ4 expression plasmid led to expression of the corresponding protein which suggests that the 5-LOΔ4 isoform is a stable protein in eukaryotic cells. We were also able to obtain soluble protein after expression in E. coli and purification. The isoform itself lacks canonical enzymatic activity as it misses the non-heme iron but it still retains ATP-binding affinity. Differential scanning fluorimetric analysis shows two transitions, corresponding to the two domains of 5-LO. Whilst the catalytic domain of 5-LO WT is destabilized by calcium, addition of calcium has no influence on the catalytic domain of 5-LOΔ4. Furthermore, we investigated the influence of 5-LOΔ4 on the activity of 5-LO WT and proved that it stimulates 5-LO product formation at low protein concentrations. Therefore regulation of 5-LO by its isoform 5-LOΔ4 might represent a novel mechanism of controlling the biosynthesis of lipid mediators.
Most available knowledge on fungal arginine metabolism is derived from studies on Saccharomyces cerevisiae, in which arginine catabolism is initiated by releasing urea via the arginase reaction. Orthologues of the S. cerevisiae genes encoding the first three enzymes in the arginase pathway were cloned from Kluyveromyces lactis and shown to functionally complement the corresponding deletion in S. cerevisiae. Surprisingly, deletion of the single K. lactis arginase gene KlCAR1 did not completely abolish growth on arginine as nitrogen source. Growth rate of the deletion mutant strongly increased during serial transfer in shake-flask cultures. A combination of RNAseq-based transcriptome analysis and 13C-15N-based flux analysis was used to elucidate the arginase-independent pathway. Isotopic 13C15N-enrichment in γ-aminobutyrate revealed succinate as the entry point in the TCA cycle of the alternative pathway. Transcript analysis combined with enzyme activity measurements indicated increased expression in the Klcar1Δ mutant of a guanidinobutyrase (EC.3.5.3.7), a key enzyme in a new pathway for arginine degradation. Expression of the K. lactis KLLA0F27995g (renamed KlGBU1) encoding guanidinobutyrase enabled S. cerevisiae to use guanidinobutyrate as sole nitrogen source and its deletion in K. lactis almost completely abolish growth on this nitrogen source. Phylogenetic analysis suggests that this enzyme activity is widespread in fungi.
Bücherschau
(1993)
Nomenklatorische Korrekturen (nach dem Artikel 43 des Codes der pflanzensoziologischen Nomenklatur) einiger Syntaxon-Namen aus den Klassen Bidentetea tripartiti, Festuco-Brometea, Koelerio-Corynephoretea and Puccinellio-Salicornietea, die wegen falsch angewandter Artnamen notwendig waren, werden begründet und durchgeführt. Die Problematik des Namens Agropyro dumetori-Artemisietum absinthii Br.-Bl. ex Kielhauser 1954 nom. invers. wird erörtert. Für einige der Namen wird die noch ausstehende Typisierung vorgenommen.
Die Pilzflora eines über 5 Jahre untersuchten, moosreichen Luzulo-Quercetum petraeae im Hamelner Stadtforst (Landkreis Hameln-Pyrmont, Niedersachsen) wird vorgestellt. Es konnte eine überdurchschnittlich hohe Zahl seltener und gefährdeter Arten festgestellt werden. Die Artenzusammensetzung wird mit vorliegenden pilzsoziologischen Untersuchungen von Buchenwald-Gesellschaften des Weserberglandes verglichen. Standortfaktoren werden diskutiert. Der hohe Wert der Fläche für den Naturschutz im Bundesland Niedersachsen wird hervorgehoben.
Aus der Drauniederung südlich Szigetvár wird die für das Fraxino pannonicae-Ulmetum Soó 1960 charakteristische Moosvegetation auf lebender Borke und morschem Holz beschrieben. Von besonderem Interesse sind Assoziationen der epiphytischen Verbände Ulotion crispae Bk. 1958, Syntrichion laevipilae Ochs. 1928, Leskeion polycarpae Bk. 1958, Neckerion complanatae Sm. et Had. in Kl. et Had. 1944, Dicrano-Hypnion filiformis Bk. 1958 sowie die morsches Holz kennzeichnenden Verbände Bryo-Brachythecion Lee. 1975 em. Mar. 1987 und Nowellion curvifoliae Phil. 1965.
Vier Acker-Unkrautgemeinschaften werden aus dem Naturraum Kraichgau beschrieben, einer trocken-warmen Löß-Hügellandschaft in Südwest-Deutschland. Die Beziehung zwischen Acker-Unkrautbeständen und landwirtschaftlicher Produktionsintensität wird über „autökologische Bautypen" (z.B. Lebensformen und Wuchsformen) analysiert. Der Therophyten-Anteil und der Anteil kleinwüchsiger Arten geht mit steigendem Herbizideinsatz zurück, während relativ dazu Geophyten mit unterirdischen Ausläufern zunehmen.
Das östliche Meißner-Vorland (Nordhessen) ist geprägt durch eine kleinflächig betriebene Nebenerwerbs-Landwirtschaft. Auf Grundlage einer floristischen Kartierung seltener Kalk-Ackerwildkräuter aus dem Jahre 1973 wurden in der Vegetationsperiode 1990 die Ackerwildkraut-Bestände floristisch und pflanzensoziologisch untersucht. Im Randbereich der Felder konnten folgende Gesellschaften nachgewiesen werden, die z.T. als Fragmente ausgebildet sind: Caucalido-Adonidetum flammeae R. Tx. 1950, Thlaspio-Veronicetum politae Görs 1966, Thlaspio-Fumarietum officinalis Görs in Oberd. et al. 1967 ex Pass, et Jurko 1975, Aphano-Matricarietum chamomillae R. Tx. 1937 em. Pass. 1957, und Spergulo-Chrysanthemetum segetum R. Tx. 1937.
Das Papaveretum argemones (Libb. 1932) Krusem. et Vlieg. 1939 läßt sich im Gebiet nicht als eigene Gesellschaft fassen; seine Kennarten sind mit den Arten der Kalkäcker vergesellschaftet. Auf mehrjährig stillgelegten Flächen finden sich Sukzessionsstadien, die zu Grünland-Gesellschaften überleiten. Die Wuchsorte einiger seltener Ackerwildkräuter in den Jahren 1975 und 1990 werden anhand von Verbreitungskarten gegenübergestellt und Entwicklungstendenzen diskutiert. Das nachwievor bemerkenswert reiche Arteninventar vieler Felder ist durch Intensivierungsmaßnahmen, zunehmend aber auch durch die Aufgabe der Ackernutzung bedroht. Perspektiven einer Erhaltung der Artenvielfalt werden diskutiert.
We report on HCFC-22 data acquired by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) in reduced spectral resolution nominal mode in the period from January 2005 to April 2012 from version 5.02 level-1b spectral data and covering an altitude range from the upper troposphere (above cloud top altitude) to about 50 km. The profile retrieval was performed by constrained nonlinear least squares fitting of measured limb spectral radiances to modelled spectra. The spectral v4-band at 816.5 ± 13 cm-1 was used for the retrieval. A Tikhonov-type smoothing constraint was applied to stabilise the retrieval. In the lower stratosphere, we find a global volume mixing ratio of HCFC-22 of about 185 pptv in January 2005. The linear growth rate in the lower latitudes lower stratosphere was about 6 to 7 pptv yr-1 in the period 2005–2012. The obtained profiles were compared with ACE-FTS satellite data v3.5, as well as with MkIV balloon profiles and in situ cryosampler balloon measurements. Between 13 and 22 km, average agreement within -3 to +5 pptv (MIPAS–ACE) with ACE-FTS v3.5 pro files is demonstrated. Agreement with MkIV solar occultation balloon-borne measurements is within 10–20 pptv below 30 km and worse above, while in situ cryosampler balloon measurements are systematically lower over their full altitude range by 15– 50 pptv below 24 km and less than 10 pptv above 28 km. Obtained MIPAS HCFC-22 time series below 10 km altitude are shown to agree mostly well to corresponding time series of near-surface abundances from NOAA/ESRL and AGAGE networks, although a more pronounced seasonal cycle is obvious in the satellite data, probably due to tropopause altitude fluctuations and subsidence of polar winter stratospheric air into the troposphere. A parametric model consisting of constant, linear, quasi-biennial oscillation (QBO) and several sine and cosine terms with different periods has been fitted to the temporal variation of stratospheric HCFC-22 for all 10° latitude/1 to 2 km altitude bins. The relative linear variation was always positive, with relative increases of 40–70%decade-1 in the tropics and global lower stratosphere, and up to 120%decade-1 in the upper stratosphere of the northern polar region and the southern extratropical hemisphere. In the middle stratosphere between 20 and 30 km, the observed trend is not consistent with the age of stratospheric air-corrected trend at ground, but stronger positive at the Southern Hemisphere and less strong increasing in the Northern Hemisphere, hinting towards changes in the stratospheric circulation over the observation period.