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921.
A methanogen (strain NaT1) that belongs to the family of Methanosarcinaceae and that can grow on tetramethylammonium as the
sole energy source has recently been isolated. We report here that cell extracts of the archaeon catalyze the formation of
methyl-coenzyme M from coenzyme M and tetramethylammonium. The activity was dependent on the presence of Ti(III) citrate and
ATP, and was rapidly lost under oxic conditions. Anoxic chromatography on DEAE-Sepharose revealed that two fractions, fractions
3 and 4, were required for activity. A 50-kDa protein that together with fraction 3 catalyzed methyl-coenzyme M formation
from tetramethylammonium and coenzyme M was purified from fraction 4. From fraction 3, a 22-kDa corrinoid protein and a 40-kDa
protein exhibiting methylcobalamin:coenzyme M methyltransferase (MT2) activity were purified. The N-terminal amino acid sequences
of these purified proteins were determined. The 40-kDa protein showed sequence similarity to MT2 isoenzymes from Methanosarcina barkeri. Cell extract of strain NaT1 grown on trimethylamine rather than on tetramethylammonium did not exhibit tetramethylammonium:coenzyme
M methyltransferase activity. The strain was identified as belonging to the genus of Methanococcoides, its closest relative
being Methanococcoides methylutens.
Received: 7 April 1998 / Accepted: 26 June 1998 相似文献
922.
Physiological and Molecular Biological Characterization of Ammonia Oxidation of the Heterotrophic Nitrifier Pseudomonas putida 总被引:2,自引:0,他引:2
Michael Daum Wolfgang Zimmer Hans Papen Karin Kloos Kerstin Nawrath Hermann Bothe 《Current microbiology》1998,37(4):281-288
The heterotrophic nitrifier Pseudomonas putida aerobically oxidized ammonia to hydroxylamine, nitrite, and nitrate. Product formation was accompanied by a small but significant
release of NO, whereas N2O evolution could not be detected under the assay conditions employed. The isolate reduced nitrate to nitrite and partially
further to NO under anaerobic conditions. Aerobically grown cells utilized γ-aminobutyrate as a carbon source and as a N-source
by ammonification. The physiological experiments, in particular the inhibition pattern by C2H2, indicated that P. putida expressed an ammonia monooxigenase. DNA-hybridization with an amoA gene probe coding for the smaller subunit of the ammonia monooxigenase of Nitrosomonas europaea allowed us to identify, to clone, and to sequence a region with an open reading frame showing distinct sequence similarities
to the amoA gene of autotrophic ammonia oxidizers.
Received: 9 April 1998 / Accepted: 15 May 1998 相似文献
923.
Silvano De Bernardo Manfred Weigele Voldemar Toome Karin Manhart Willy Leimgruber Peter Böhlen Stanley Stein Sidney Udenfriend 《Archives of biochemistry and biophysics》1974,163(1):390-399
Fluorescamine is a useful reagent for the fluorometric assay of primary amines. The extent of the reaction between fluorescamine and primary amines, as well as the fluorescence intensities of the resulting fluorophors depend on pH, solvent composition and reagent concentration. Optimum values for these variables further depend on the amine under study. The influence of these parameters on the fluorogenic reaction of representative amines, and on their fluorophoric derivatives has been investigated, and the results are reported here. 相似文献
924.
Fourteen women taking oral contraceptives were admitted during a five-year period because of acute cerebrovascular lesions. A diagnosis of major cerebral embolism was established in four of them. No source of embolism was found, and thorough investigation failed to reveal any predisposing illness. Cerebral embolism was a probable diagnosis in several of the remaining 10 patients. A comparison was made with the strokes occurring in women not taking contraceptive pills in corresponding age groups. 相似文献
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