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141.
142.
H+/sugar symport in the obligatory aerobic yeastRhodotorula glutinis was analyzed under conditions where the plasma membrane was selectively depolarized by the lipophilic cation tetraphenylphosphonium (TPP+). Control experiments showed that this treatment did not impair the transmembrane pH, the cell energy charge, and the function of plasma membrane H+-ATPase. The kinetic data were fitted to elementary functions derived from a model constructed on the basis of some simplifying premises for ordered (either C + H+ + S or C + S + H+) and random reaction mechanisms. In addition, the comparison of the kinetic parameters in fully energized and depolarized cells provided information about the free carrier charge. It was concluded that the binding sequence of formation of the ternary carrier/H+/substrate complex follows a random mechanism and that the carrier bears a negative charge. 相似文献
143.
144.
145.
146.
Wolfgang Witt Peter Hampel Klaus Böcker Angelika Mertsching 《Archives of microbiology》1989,151(2):154-158
Divalent cations activate the lysophospholipase and transacylase reactions catalyzed by the same enzymes in the yeast Saccharomyces cerevisiae. The activation was observed at neutral pH, but not at the pH optimum of lysophospholipase/transacylase, near 3.5. Adenine nucleotides, especially AMP and ADP, are strong inhibitors of the same group of enzymes. Half maximal inhibition by AMP was found at a concentration of about 20 M. The inhibition by nucleotides in low concentrations is enhanced by divalent cations. 相似文献
147.
Archaeoglobus fulgidus is an extremely thermophilic archaebacterium that can grow at the expense of lactate oxidation with sulfate to CO2 and H2S. The organism contains coenzyme F420, tetrahydromethanopterin, and methanofuran which are coenzymes previously thought to be unique for methanogenic bacteria. We report here that the bacterium contains methylenetetrahydromethanopterin: F420 oxidoreductase (20 U/mg), methenyltetrahydromethanopterin cyclohydrolase (0.9 U/mg), formyltetrahydromethanopterin: methanofuran formyltransferase (4.4 U/mg), and formylmethanofuran: benzyl viologen oxidoreductase (35 mU/mg). Besides these enzymes carbon monoxide: methyl viologen oxidoreductase (5 U/mg), pyruvate: methyl viologen oxidoreductase (0.7 U/mg), and membranebound lactate: dimethylnaphthoquinone oxidoreductase (0.1 U/mg) were found. 2-Oxoglutarate dehydrogenase, which is a key enzyme of the citric acid cycle, was not detectable. From the enzyme outfit it is concluded that in A. fulgidus lactate is oxidized to CO2 via a modified acetyl-CoA/carbon monoxide dehydrogenase pathway involving C1-intermediates otherwise only used by methanogenic bacteria.Non-standard abbreviations APS
adenosine 5-phosphosulfate
- BV
benzyl viologen
- DCPIP
2,6-dichlorophenolindophenol
- DMN
2,3-dimethyl-1,4-naphthoquinone
- DTT
DL-1,4-dithiothreitol
- H4F
tetrahydrofolate
- H4MPT
tetrahydromethanopterin
- CH2
H4MPT, methylene-H4MPT
- CH
H4MPT, methenyl-H4MPT
- Mes
morpholinoethane sulfonic acid
- MFR
methanofuran
- Mops
morpholinopropane sulfonic acid
- MV
methyl viologen
- Tricine
N-tris(hydroxymethyl)-methylglycine
- U
mol product formed per min 相似文献
148.
Christiane Wloczyk Achim Kröger Thomas Göbel Gabriele Holdt Ralf Steudel 《Archives of microbiology》1989,152(6):600-605
Wolinella succinogenes grown on formate and elemental sulphur was found to use the polysulphide derivatives 2,2-tetrathiobispropionate (R2S4) or pentathionate (S5O
6
=
) as acceptors for formate oxidation. The specific activities of formate oxidation with these acceptors were similar to those with elemental sulphur. The main reaction products of R2S4 reduction were 2,2-dithiobispropionate (R2S2) and sulphide. Pentathionate was converted to thiosulphate and some elemental sulphur. The electrochemical proton potential
across the cytoplasmic membrane of the bacterium was measured in the steady state of electron transport from formate to R2S4. The electrical proportion () of the
determined through the distribution of labeled tetraphenylphosphonium cation was obtained as 0.17 Volt. The was zero, when a protonophore was present. The pH-difference across the membrane was negligible. Thus the
generated by sulphur respiration is close to that measured earlier with fumarate as the terminal acceptor of electron transport.Abbreviations DMO
5,5-dimethyloxazolidine-2,4-dione
- R2Sn (n=2–5)
2,2-polythiobispropionate
- TTFB
4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazol
- TPP
tetraphenylphosphonium cation 相似文献
149.
A new strain of the green sulfur bacteria was isolated from the monimolimnion of Buchensee (near Radolfzell, Lake Constance region, FRG). Single cells were rod-shaped, nonmotile and contained gas vacuoles. Typical net-like colonies were formed by ternary fission of the cells. As photosynthetic pigments bacteriochlorophylls a, e, isorenieratene and -isorenieratene were present. Sulfide, sulfur and thiosulfate were used as electron donors during anaerobic phototrophic growth. Besides carbon dioxide, acetate and propionate could serve as carbon sources under mixotrophic conditions in the light. Like all other members of the green sulfur bacteria, the new bacterium is strictly anaerobic and obligately phototrophic. The possession of gas vacuoles and the formation of net-like colonies and the guanine plus cytosine content of the DNA (47.9 mol% G+C) are typical characteristics of the genus Pelodictyon. Because of its photosynthetic pigments which differ from those of Pelodictyon clathratiforme, strain BU 1 represents a new species, P. Phaeoclathratiforme sp. nov. 相似文献
150.
I. M. Birk R. Dierstein I. Kaiser U. Matern W. A. König R. Krebber J. Weckesser 《Archives of microbiology》1989,151(5):411-415
Toxic and nontoxic peptides were isolated from the cyanobacterium Microcystis aeruginosa PCC 7806 by a procedure including extraction of cells with water-saturated 1-butanol, chromatography of the extract on silica
gel plates and high performance liquid chromatography (HPLC) on Partisil-5. The toxin was shown to be only a minor constituent,
being negatively charged and thus separable by electrophoresis, within the HPLC-purified fraction. It contained erythro-β-methyl-D-Asp, D-Glu, D-Ala, L-Leu, and L-Arg known to be part of the Microcystis peptide-toxin with Mr 994. The major part of the HPLC-purified fraction was assigned, however, to a nontoxic peptide with a Mr of 956. Partial hydrolysis studies of the nontoxic peptide(s) revealed amino acid sequences composed of D-Glu, N-methyl-Phe, and 3,4-dehydro-Pro, aside from the common L-amino acids. Cyclic linkage in the nontoxic peptide(s) appears likely. 相似文献