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991.
992.
993.
Simultaneous induction of two enzymes sensitive to catabolite repression does not lead to an additive decrease of the specific activity of the two. Exogenously added cAMP increases the specific activity of catabolically repressed enzymes, irrespective of whether the enzyme is induced separately or simultaneously with another enzyme. In the presence of 12 different substrates metabolized by inducible enzymes glucose does not bring about catabolite repression. Synthesis of cAMP is identical with that occurring under conditions when glucose brings about catabolite repression. 相似文献
994.
Mutants ofOudemansiella mucida, blocked in the biosynthesis of the antibiotic mucidin, were obtained at a 0.28 % frequency after the application of N-methyl-N’-nitro-N-nitrosoguanidine (MNG) to basidiospores under conditions leading to 0.5–5.0 % survival rates. Loss of antibiotic activity was in most isolates accompanied by a decrease in mycelium growth rate and a suppression of dikaryotizing and fructification ability. Recombination analysis of two stable mutants revealed that the block in mucidin synthesis is the result of mutation in the same chromosomal gene(muc). In contrast to the action of MNG, UV-irradiation leads neither to the loss of biosynthetic activity nor to any morphological change. 相似文献
995.
The effect of 1-dodecylpiperidine 1-oxide and N,N’-bis(dodecyldimethyl)-1,2-ethane diammonium dibromide on the spores ofBacillus cereus. particularly their binding to intact spores and spores with reduced cystine bonds, was investigated. The Langmuir type of binding is involved in both cases. Both compounds decreased the thermoresistance of spores. DPNO decreased the fraction of non-germinating spores, the effect of the drug increasing with increasing concentration. This phenomenon was associated with a faster release of dipicolinic acid to the medium. Only microgermination proceeded in the presence of BDED and dipicolinic acid was released only in substantially lower amounts. Both compounds also influenced respiration. 相似文献
996.
A lipopolysaccharide was isolated by extraction ofAspergillus flavus conidia with 45 % phenol at 68–70 °C. Quantitative analysis revealed 7 % nucleic acids, 5.5 % proteins, 46 % polysaccharides and 49 % lipids, of which 12 % were covalently bound. Glucose, mannose, galactose and fucose were detected as monosaccharide components of the polysaccharide moiety by gas chromatography; palmitic acid, stearic acid, oleic acid, linoleic acid and myristic acid were mainly present in the lipidic fraction. This material differs from the bacterial lipopolysaccharides, both in composition of the polysaccharide moiety and representation of fatty acids in the lipidic fraction. 相似文献
997.
Heterogeneity of glutamine synthetase polypeptides in Neurospora crassa 总被引:11,自引:0,他引:11
F Sánchez E Calva M Campomanes L Blanco J Guzmán J L Saborío R Palacios 《The Journal of biological chemistry》1980,255(6):2231-2234
Purified preparations of Neurospora crassa glutamine synthetase contain two nonidentical polypeptides that can be separated by acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and 7 M urea. These polypeptides are synthesized both in vivo and in a heterologous cell-free protein-synthesizing system. The data presented indicate that both polypeptides contain an active site for glutamine synthetase activity and suggest that there is not a precursor-product relationship between them. 相似文献
998.
J A Gil P Liras G Naharro J R Villanueva J F Martín 《Journal of general microbiology》1980,118(1):189-195
The biosynthesis by Streptomyces griseus of candicidin, an aromatic polyene macrolide antibiotic, was inhibited by L-tryptophan, L-phenylalanine and, to a lesser degree, by L-tyrosine. A mixture of the three aromatic amino acids inhibited candicidin biosynthesis to a greater extent than did each amino acid separately. L-Tryptophan strongly inhibited the incorporation of the labelled precursors propionate or 4-aminobenzoic acid into candicidin. Incorporation of propionate into candicidin was 50% inhibited by 2.5 mM-tryptophan. Inhibition by tryptophan did not require protein synthesis as the same effect was observed in cells in which protein synthesis was prevented by chloramphenicol. The inhibitory effect of L-tryptophan was partially reversed by exogenous 4-aminobenzoic acid suggesting that this effect is exerted at the level of 4-aminobenzoic acid synthase. 相似文献
999.
L Kovác I Gbelská V Poliachová J Subík V Kovácová 《European journal of biochemistry》1980,111(2):491-501
A single-gene nuclear choline-requiring mutant of Saccharomyces cerevisiae was studied. Choline as a growth supplement to synthetic media could be substituted by low concentrations of dimethylethanolamine, monomethylethanolamine or ethanolamine. DL-Serine also supported growth, but only at high concentrations: on a molar basis it was approximately one hundred times less effective than choline. When cultured in unsupplemented medium the mutant cells soon ceased to grow. The growth-arrested cells contained less than one fifth of the phosphatidylethanolamine present in wild-type cells and only traces of phosphatidylserine. The relative content of the two phospholipid species was raised by growing the mutant cells in the presence of choline of the other supplements but still remained lower than in wild-type cells. The mutant cells depleted of phosphatidylethanolamine and phosphatidylserine had greatly diminished ability to fuse with other cells in mating and their protoplasts showed increased resistance to hypotonic lysis. Respiration was not substantially affected by the deficit of the two phospholipid species in the mutant. In cell-free preparations, the affinity of the phosphatidylserine synthesizing system for serine was found to be almost two orders of magnitude lower in the mutant than in the wild-type. The impairment of phosphatidylserine synthesis accounts for growth requirement and the abnormal phospholipid composition of the mutant cells. 相似文献
1000.