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O B Astaurova

Publications and source records attributed to O B Astaurova.

10 recordsLinked to original sources
PubMed1999

Isolation and primary characterization of an amidase from Rhodococcus rhodochrous.

Amidase (EC 3.5.1.4) was purified to homogeneity from Rhodococcus rhodochrous M8 using isopropanol fractionation and exchange chromatography on Mono Q. The isolated amidase consists of four identical subunits with molecular weight 42+/-2 kD. The activity of the enzyme is maximal at 55-60 degrees C and within the pH range 5-8. The amidase from R. rhodochrous M8 is highly sensitive to such sulfhydryl reagents as Hg2+ and Cu2+. Chelators (EDTA and o-phenanthroline) and serine proteinase inhibitors (PMSF and DIFP) did not inhibit the activity of the enzyme. The enzyme exhibits hydrolytic and acyl transferase activity and does not possess urease activity. Aliphatic amides (acetamide and propionamide) were the best substrates for the amidase from R. rhodochrous M8, whereas bulky aromatic amides were poor substrates of this enzyme. The properties of the isolated enzyme are similar to those found in the corresponding amidase from Arthrobacter sp. J-1 and an amidase with wide substrate specificity from Brevibacterium sp. R312.

Amidohydrolases↗
PubMed1977

[Isoenzyme makeup of the malate dehydrogenase in 2 species of Acetabularia].

The isozymes of malate dehydrogenase (MDH) were studied by means of electrophoresis in polyacrilamide gel in Acetabularia crenulata and A. mediterranea. The isozyme profile of MDH was shown to be variable in different parts of the plant. Distinct differences in isozyme profiles of MDH between A. crenulata and A. mediteranea were found when studying the cell fractions which consisted mainly of chloroplasts. The chloroplast fraction of A. mediterranea contained 8 isozymes which form 2 groups with different electrophoretic mobility. The chloroplast fraction of A. crenulata contained 9 isozymes. All the isozymes of the first group were common for both the species under study.

Acetabularia↗
PubMed1977

[Malate dehydrogenase isoenzyme induction in an Acetabularia chloroplast fraction with nuclear transplants].

Changes in isozymes of malate dehydrogenase (MDH) in the chloroplast fraction under the transplantation of the A. crenulata nuclei in the A. mediterranea anuclear fragments were studied by means of electrophoresis in polyacrilamide gel. Within 30 days after the transplantation the nucleus induces in the chloroplast fraction MDH isozymes similar by the electrophoretic mobility with those of A. crenulata. The induction of such isozymes was observed both in the plants with the morphological characters of A. crenulata and the fragments which have not formed the reproductive caps, as well as under the transplantation of a small amount of cytoplasm from A. crenulata with chloroplasts in the anuclear fragments of A. mediterranea.

Acetabularia↗
PubMedDate not supplied

[Adaptation of acrylamide producer Rhodococcus rhodochrous M8 to change in ammonium concentration in medium].

The mechanism of adaptation of the acrylamide producing strain Rhodococcus rhodochrous M8 to changes in ammonium concentrations in the medium was studied. An increase in the content of ammonium in the medium changed the activity of glutamine synthetase (GS) (EC 6.3.1.2) and glutamine dehydrogenase (GD) (EC 1.4.1.4), the enzymes of ammonium assimilation, as well as the activities of enzymes responsible for nitrile utilization: nitrile hydratase (EC 4.2.1.84) and amidase (EC 3.5.1.4). This also caused inhibition of activation of GS induced by phosphodiesterase (EC 3.1.4.1). Increases in the activities of nitrile hydratase and amidase and resistance of these enzymes to ammonium were observed in mutant of R. rhodichrous resistant to phosphotricine, an inhibitor of GS. An important role of GS in the mechanism of adaptation is suggested.

Acrylamide↗
PubMedDate not supplied

[Quorum-sensing regulation in soil pseudomonads].

228 strains of soil and rhizosphere pseudomonads isolated in different geographic zones were screened, with the use of two tester systems, for the capacity to produce N-acetyl-homoserine lactones (AHLs), which are autoinducers involved in quorum-sensing (QS) regulation. AHL production was found in 11.4% of the strains investigated. In five Pseudomonas chlororaphis strains shown to be active AHL producers and chosen for further study, PCR identified two QS systems that involved the phzI, phzR, csaI, and csaR genes; this finding suggests the conservative nature of these regulation systems in P. chlororaphis. Strain P. chlororaphis 449, chosen as a model object and studied in greater detail, produced three AHL species including N-butanoyl-homoserine lactone and N-hexanoyl-homoserine lactone. This strain produced three types of phenazine antibiotics, as well as siderophores and cyanide; it also exhibited antagonistic properties toward a wide spectrum of phytopathogenic fungi. The phzI and csaI genes, coding for synthases of AHLs of two types, were cloned and sequenced; mutants with knocked-out phzI and csal genes were obtained. With the use of transposon mutagenesis and the gene substitution method, mutations were obtained in the global expression regulator genes gacS, coding for the GacA-GacS regulation system kinase, and rpoS, coding for the sigma S subunit of RNA polymerase. The effect of these mutations on the AHL synthesis and on the regulation of various metabolic processes in P. chlororaphis was studied.

4-Butyrolactone↗
PubMedDate not supplied

[Comparative study of E. coli strains producing amino acids].

Transduction of the locus of stability to high threonine concentrations (Thrr) into E. coli str M1 and C600 resulted in enhancements of the amino acid production and retardation of the culture development. Besides the mutation caused increase of the specific activity of glutamate synthase, aspartate kinase and homoserine dehydrogenase. The cells of the mutant strains had poorly developed walls and were smaller than those of the parent strains.

Amino Acids↗
PubMedDate not supplied

[Amination in E. coli strains effectively producing threonine].

The effect of the mutation of threonine and homoserine resistance (thrr) on the activity of the enzymes catalysing the biosynthesis of glutamic acid, glutamate synthase (EC 1.4.1.13) and glutamate dehydrogenase (EC 1.4.1.4), and on the productivity of a threonine-producing E. coli strain obtained by gene engineering was being studied. The resistance to threonine was found to correlate well with the increasing activities of the abovementioned enzymes and with a higher productivity of the E. coli strain.

Culture Media↗
PubMedDate not supplied

[Amination and biosynthesis of glutamate by R- and S-forms of Bacillus thuringiensis].

These studies were designed to determine the biochemical nature of the Bacillus thuringiensis growth being dependent on glutamate during cultivation in a minimal medium. This is possible to be due to the absence of enzymes which catalyze glutamic acid synthesis by direct amination of alpha-ketoglutaric acid, glutamate dehydrogenase and glutamate synthase, and a decrease in the activity of the enzyme catalyzing amination of pyruvic acid, alanine dehydrogenase. It has been shown that the lack of glutamate can be compensated by histidine and proline; in this case, the growth efficiency of R form is greater than that of S form which is consistent with an increased rate of protein synthesis of R form.

Alanine↗