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101.
Francisco Javier Caballero Isabel Igeño Jacobo Cárdenas Francisco Castillo 《Archives of microbiology》1989,152(5):508-511
The phototrophic bacterium Rhodobacter capsulatus E1F1 assimilates ammonia and other forms of reduced nitrogen either through the GS/GOGAT pathway or by the concerted action of l-alanine dehydrogenase and aminotransferases. These routes are light-independent and very responsive to the carbon and nitrogen sources used for cell growth. GS was most active in cells grown on nitrate or l-glutamate as nitrogen sources, whereas it was heavily adenylylated and siginificantly repressed by ammonium, glycine, l-alanine, l-aspartate, l-asparagine and l-glutamine, under which conditions specific aminotransferases were induced. GOGAT activity was kept at constitutive levels in cells grown on l-amino acids as nitrogen sources except on l-glutamine where it was significantly induced during the early phase of growth. In vitro, GOGAT activity was strongly inhibited by l-tyrosine and NADPH. In cells using l-asparagine or l-aspartate as nitrogen source, a concerted induction of l-aspartate aminotransferase and l-asparaginase was observed. Enzyme level enhancements in response to nitrogen source variation involved de novo protein synthesis and strongly correlated with the cell growth phase.Abbreviations ADH
l-alanine dehydrogenase
- AOAT
l-alanine:2-oxoglutarate aminotransferase
- Asnase
l-asparaginase
- GOAT
Glycine: oxaloacetate aminotransferase
- GOGAT
Glutamate synthase
- GOT
l-aspartate: 2-oxoglutarate aminotransferase
- GS
Glutamine synthetase
- HPLC
High-Pressure Liquid Chromatography
- MOPS
2-(N-morpholino)propanesulfonic acid
- MSX
l-methionine-d,l-sulfoximine 相似文献
102.
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
103.
104.
Fucosidosis is an autosomal recessive lysosomal storage disease due to a deficiency of-L-fucosidase activity in tissues and body fluids. Exponentially growing lymphoid cell cultures from four fucosidosis patients had 2.7-fold to 15.6-fold less extracellular-L-fucosidase protein and 28.8-fold to 144.0-fold less intracellular-L-fucosidase protein with negligible catalytic activity, compared to the mean of 19 control cultures. The percentage of total-L-fucosidase protein released extracellularly by cultures from the four patients was 64 to 85%, compared to 35±9% for control cultures. Intracellular and extracellular enzyme forms in fucosidosis and control cell lines were glycoproteins containing polypeptide chains ofM
r=52,000. During a 1.5-hr pulse-label with35S-methionine,-L-fucosidase was synthesized by control cells and two fucosidosis cell lines as an intracellular form withM
r=58,000. During a subsequent 21-hr chase with unlabeled methionine, mutant enzyme was almost entirely processed to an extracellular form withM
r=62,000. In contrast, only 25–30% of control enzyme was processed to an extracellular form (M
r=62,000), with the remainder retained intracellularly (M
r=60,000). In the other two fucosidosis cell lines,-L-fucosidase was synthesized as an intracellular form withM
r=56,000 that was processed to an extracellular form withM
r=60,000. In summary, the fucosidosis mutation(s) affected the catalytic activity, quantity, and extracellular release of-L-fucosidase as expressed by lymphoid cells.This work was funded by NIH Grants DK 32161 to R. A. DiCioccio and GM 28428 to J. K. Darby. 相似文献
105.
The monofunctional thiol reagents N-ethylmaleimide (NEM) and methyl methanethiosulfonate (MMTS) stimulate ouabain resistant (OR) electroneutral K:Cl cotransport in LK sheep red blood cells at low, but not at high concentrations. Diamide (DM), on the other hand, only stimulates OR K:Cl flux (Lauf, P.K., J. Memb. Biol. 101: 179–188, 1988). The DM stimulated K:Cl cotransport was decreased toward the control value prior to DM stimulation when NEM or MMTS were added, subsequently. The inhibitory effect was dependent on the compound's concentration and exposure time and, in the case of MMTS, was reversed upon addition of dithiothreitol (DTT). The inhibition was more prominent when NEM treatment was performed at pH 8.0 and disappeared at pH 6.0. In contrast the NEM stimulatory effect was most effective when the pH of NEM treatment was 6.0 (Bauer, J. & Lauf, P.K., J. Memb. Biol. 73: 257–261, 1983). The results suggest the existence of additional, however, inhibitory thiol groups in the already thiol-activated K:Cl cotransporter, with a different pKa value and a lower affinity for NEM or MMTS as compared to the stimulatory thiol groups. Like the activating thiols, the inhibitory sulfhydryls appeared to be inaccessible to non-penetrating thiol reagents and hence, must be located deeper within the red cell membrane. 相似文献
106.
Eckhard Fischer Birgit Strehlow Dieter Hartz Volkmar Braun 《Archives of microbiology》1990,153(4):329-336
After uptake of microbial ferrisiderophores, iron is assumed to be released by reduction. Two ferrisiderophore-reductase activities were identified in Escherichia coli K-12. They differed in cellular location, susceptibility to amytal, and competition between oxygen and ferrichrome-iron(III) reduction. The ferrisiderophore reductase associated with the 40,000×g sediment (membrane-bound enzyme) was inhibited by 10 mM amytal in contrast to the ferrisiderophore reductase present in the 100,000×g supernatant (soluble enzyme). Reduction by the membrane-bound enzyme followed sigmoid kinetics, but was biphasic in the case of the soluble enzyme. The soluble reductase could be assigned to a protein consisting of a single polypeptide of M
r
26000. Reduction of iron(III) by the purified enzyme depended on the addition of NADH or NADPH which were equally active reductants. The cofactor FMN and to a lesser degree FAD stimulated the reaction. Substrate specificity of the soluble reductase was low. In addition to the hydroxamate siderophores arthrobactin, schizokinen, fusigen, aerobactin, ferrichrome, ferrioxamine B, coprogen, and ferrichrome A, the iron(III) complexes of synthetic catecholates, dihydroxy benzoic acid, and dicitrate, as well as carrier-free iron(III) were accepted as substrates. Both ferrisiderophore reductases were not controlled by the fur regulatory system and were not suppressed by anaerobic growth.Abbreviations DHB
dihydroxybenzoic acid
- MECAM
1,3,5-N,N,N-tris-(2,3-dihydroxybenzoyl)-triamino-methylbenzene
- MECAMS
2,3-dihydroxy-5-sulfonyl-derivative of MECAM 相似文献
107.
Frans P. Houwen Jeannette Plokker Alfons J. M. Stams Alexander J. B. Zehnder 《Archives of microbiology》1990,155(1):52-55
Enzyme measurements were carried out with crude cell-free extracts of the propionate oxidizing coculture of Syntrophobacter wolinii and Desulfovibrio G11. Using cell-free extracts of a pure culture of Desulfovibrio G11 as a blank, most of the enzymes involved in the methylmalonyl-CoA pathway for propionate oxidation, including a propionyl-CoA: oxaloacetate transcarboxylase, were demonstrated in S. wolinii. 相似文献
108.
大鼠缰核与下丘脑外侧区在调节心血管活动方面的机能联系 总被引:6,自引:0,他引:6
电刺激大鼠下丘脑外侧区(LH),动脉压明显升高,心率加快,在刺激电极同侧缰核(Hb)内微量注射盐酸利多卡因、电刺激LH引起的升压反应可被阻断38.9%,心率增快反应可被阻断44.4%,双侧Hb内微量注射盐酸利多卡因,电刺激LH引起的升压反应可被阻断40.7%,心率增快反应可被阻断41.2% ,单侧或双侧Hb内微量注射人工脑脊液均不能阻断电刺激LH引起的心血管反应。电刺激大鼠Hb,动脉压明显升高,心率无明显改变,在刺激电极同侧LH内微量注射盐酸利多卡因,电刺激Hb引起的升压反应可被阻断63.2%,双侧LH内微量注射盐酸利多卡因,电刺激Hb引起的升压反应可被阻断62.6%,单侧或双侧LH内微量注射人工脑脊液均不能阻断电刺激Hb引起的心血管反应。本实验提示Hb与LH在调节心血管活动方面有协同作用。 相似文献
109.
W. J. J. van den Tweel M. N. Widjojoatmodjo J. A. M. de Bont 《Archives of microbiology》1988,150(5):471-476
Thirteen bacteria were isolated on D-4-hydroxyphenylglycine as sole carbon and energy source. Seven strains transaminated only the D-enantiomer while the other six isolates transaminated both enantiomers of 4-hydroxyphenylglycine. One of the six strains utilizing both enantiomers was characterized as a Pseudomonas putida. This strain, MW27, employed two enantioselective transaminases, to catalyze the initial step in the metabolism of DL-4-hydroxyphenylglycine. The product of the transamination, 4-hydroxyphenylglyoxylate, was further metabolized via 4-hydroxybenzaldehyde and 4-hydroxybenzoate to protocatechuate. Preliminary results indicate that both transaminases are co-ordinately synthesized together with the 4-hydroxyphenylglyoxylate decarboxylase and the NADP+-dependent 4-hydroxybenzaldehyde dehydrogenase. 相似文献
110.
A degradation pathway for dl--phenylhydracrylic, phenylacetic, 3- and 4-hydroxyphenylacetic acid by a Flavobacterium is presented. Experiments with washed cells and enzyme studies revealed that dl--phenylhydracrylic acid in an initial reaction was oxidatively decarboxylated to phenylacetaldehyde. Whole cells oxidized both stereoisomers of phenylhydracrylic acid at different rates. The product phenylacetaldehyde in turn was oxidized to phenylacetic acid. No hydroxylation of phenylacetic acid was detected in cell extracts, but on the basis of experiments with washed cells it is assumed that phenylacetic acid is mainly metabolized via 3-hydroxyphenylacetic acid. This latter product was subsequently hydroxylated yielding the ring-cleavage substrate homogentisate. 4-Hydroxyphenylacetic acid was also degraded via homogentisate. Ringcleavage of homogentisate gave maleylacetoacetate which was further degraded through a glutathione-dependent pathway. Homoprotocatechuate was not an intermediate in the metabolism of dl-phenylhydracrylic acid, phenylacetic, 3- and 4-hydroxyphenylacetic acid metabolism, but it could be hydroxylated aspecifically to 2,4,5-trihydroxyphenylacetic acid by the action of the 3-hydroxyphenylacetic acid-6-hydroxylase.Abbreviations HPLC
high-performance liquid chromatography
- PHA
phenylhydracrylic acid
- PA
phenylacetic acid
- HPA
hyxdroxyphenylacetic acid
- PMS
phenazine methosulphate
- PMA
phenylmalonic acid
- GSH
glutathione 相似文献