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Biomedical subjects

E Curdová

Publications and source records attributed to E Curdová.

8 recordsLinked to original sources
PubMed1991

Immunomodulators isolated from microorganisms.

Microbial products are surveyed that have an immunoregulatory activity, both from the realm of low-molar-mass compounds and from the group of naturally occurring polymers. The data include in most cases the producer organism or source, a brief chemical characteristic and biological activity. Various groups of substances are compared, the drawbacks attendant on their acquisition and application are pointed out and their advantageous properties are specified.

Adjuvants, Immunologic↗
PubMed1989

The effect of inorganic phosphate on the production of avermectin in Streptomyces avermitilis.

The effect of phosphate on the production of avermectin B1a, growth and utilization of glucose in the course of cultivation of Streptomyces avermitilis on a complex and chemically defined medium has been studied. Phosphate added at the beginning of cultivation at 1-20 mmol/l did not distinctly affect the production of secondary metabolite. From the results it follows that the biosynthesis of avermectin tolerates high concentrations of phosphate in the medium.

Anthelmintics↗
PubMed1982

Role of phosphatases in the biosynthesis of chlortetracycline in Streptomyces aureofaciens.

ATP diphosphohydrolase activity and inorganic pyrophosphatase reached two maxima during cultivation of the low- and high-producing variant of Streptomyces aureofaciens under conditions of phosphate limitation, i.e. after 30 and 70 h of cultivation. Increased levels of inorganic phosphate in a medium inhibitory to biosynthesis of chlortetracycline markedly decreased the levels of both enzymes. The ATP diphosphohydrolase activity was detected both in the supernatant and membrane fractions of the cell-free preparation of the mycelium.

Apyrase↗
PubMed1982

Properties of apyrase and inorganic pyrophosphatase in Streptomyces aureofaciens.

Apyrase (ATP-diphosphohydrolase, EC 3.6.1.5) and inorganic pyrophosphatase (EC 3.6.1.1) were partially purified from S. aureofaciens RIA 57 and characterized. Apyrase degrades, in addition to ATP, other nucleoside triphosphates and nucleoside diphosphates, diphosphate, thiamine diphosphate, phosphoenolpyruvate and oligophosphates of chain length n less than 90. The apyrase activity was detected in the membrane and supernatant fractions. Its properties (substrate specificity. effect of inhibitors, pH optimum and effect of Mg2+ ions) were similar in both fractions except for the effect of oligomycin that inhibited only the membrane fraction. Pyrophosphatase exhibited a strict substrate specificity, substrates other than diphosphate being degraded relatively slowly. Of other enzymes exhibiting the phosphatase activity acid phosphatase (EC 3.1.3.2) and alkaline phosphatase (EC 3.1.3.1), trimetaphosphatase (EC 3.6.1.2) and exopolyphosphatase (EC 3.6.1.11) degrading oligophosphatase of chain length n = 15, 40 and 60, were detected.

Adenosine Triphosphate↗
PubMed1979

[Action of chlortetracycline on the enzymes of the producer itself, Streptomyces aureofaciens].

When preparing a cell-free extract of Streptomyces aureofaciens from the culture to which chlortetracycline (1000 gamma/ml) was added before disintegration with alumina, a considerable decrease in the enzyme activity was reached. The presence of chlortetracycline during disintegration of the cells by means of glass beads did not substantially affect the enzyme activity of the cell-free extract. Addition of chlortetracycline directly to the reaction mixture for the enzyme assay (up to a concentration of 200 gamma/ml) did not induce any inhibition effect. The results suggested that during studying enzyme systems of organisms producing secondary metabolites, the product might distort the results on the use of an inconvenient method.

Cell Fractionation↗
PubMed1976

Regulation and biosynthesis of secondary metabolites. XVIII. Adenylate level and chlorotetracycline production in Streptomyces aureofaciens.

The relationship was studied between the energy metabolism of the actinomycete Streptomyces aureofaciens and the biosynthesis of chlorotetracycline by this organism. The energy charge values in a culture of low-production strain were almost identical with those of a production variant but the total sum of adenylates was about 10 times higher. In the stationary growth phase both strains evinced a drop in energy charge values followed by a rise to the original level. An increase in the concentration of inorganic phosphate in fermentation medium caused a suppression of antibiotic formation in the lowproduction strain and further rise in the total adenylate level. The expression of the energy charge in Streptomyces aureofaciens acquires a complex character owing to the participation, apart from the adenylate system, of high-molecular polyphosphates as energy donors and the probable lack of a regulating mechanism such as the adenylate kinase reaction.

Adenine Nucleotides↗