Biomedical subjects

D V Dovbnya

Publications and source records attributed to D V Dovbnya.

4 recordsLinked to original sources

PubMed2005

Mycobacterium sp. mutant strain producing 9alpha-hydroxyandrostenedione from sitosterol.

Mycobacterium sp. VKM Ac-1815D and its derivatives with altered resistance to antibacterial agents were able to produce androst-4-ene-3,17-dione (AD) as a major product from sitosterol. In this study, those strains were subjected to subsequent mutagenization by chemical agents and UV irradiation in combination with sitosterol selection pressure. The mutant Mycobacterium sp. 2-4 M was selected, being capable of producing 9alpha-hydroxyandrost-4-ene-3,17-dione (9-OH-AD) as a major product from sitosterol, with a 50% molar yield. Along with 9-OH-AD, both AD and 9alpha-hydroxylated metabolites with a partially degraded side-chain were formed from sitosterol by the mutant strain. The strain was unable to degrade 9-OH-AD, but degraded androsta-1,4-diene-3,17-dione (ADD), thus indicating a deficiency in steroid 1(2)-dehydrogenase and the presence of 9alpha-hydroxylase activity.

Androstadienes↗

PubMed2004

Extracellular 3beta-hydroxysteroid oxidase of Mycobacterium vaccae VKM Ac-1815D.

Extracellular 3beta-hydroxysteroid oxidase (SO) has been isolated from cell-free cultivation broth at the growth of Mycobacterium vaccae VKM Ac-1815D on glycerol-mineral medium in the presence of sitosterol. The enzyme is responsible for the transformation of 3beta-hydroxy-5-ene- to 3-keto-4-ene-moiety of steroids including dehydrogenation of 3beta-hydroxy function followed by delta5-->delta4 isomerization. 6-Hydroxy-4-sitosten-3-one and 6-hydroxy-4-androsten-3,17-dione were revealed among the metabolites at the incubation of the enzyme preparations with sitosterol and dehydroepiandrosterone (DHEA), respectively. The enzyme was strongly NADH or NADPH dependent. SO has been purified over 300-fold using cultivation broth concentration on hollow fibers followed by fractionation by ammonium sulphate, column chromatography on DEAE-Toyopearl, hydroxyapatite Bio-Gel HTP and double gel-filtration on Bio-Gel A 0.5 M. SDS-electrophoresis gave a molecular mass estimate of 62 +/- 4 kDa. The purified SO obeyed Michaelis-Menten kinetics, double reciprocal plots kinetics revealed Km value towards DHEA 5 x 10(-4) M. Along with SO activity, 17-hydroxysteroid dehydrogenase (17-OH SDH) and 3-ketosteroid-1(2)-dehydrogenase (1(2)-SDH) activities were detected in cell-free cultivation broth. The extracellular steroid transforming activities of C-17-ketosteroid producing mycobacteria were hitherto unreported.

3-Hydroxysteroid Dehydrogenases↗

PubMed2002

Estimation of cyclodextrin affinity to steroids.

A nonlinear spectrometric method for determination of the stability constant (Ks) for cyclodextrin complex with steroid was developed. The method is based on calculation of the parameters of competitive cyclodextrin complexation by simultaneous fitting of two types of curves. Those of the first type are the dependencies of absorbance of methyl orange solution on the cyclodextrin concentration, the second type being the absorption curves of displacement of the dye, by steroid, from the cyclodextrin complex. With the method proposed, Ks values were calculated with standard deviation less than 10%. This method is validated by determination of Ks values using the phase-solubility technique. For neutral steroid molecules, the effect of pH on Ks was found to be insignificant. Ks values for the cyclodextrin-dye complex were determined for randomly methylated beta-cyclodextrin, 2-hydroxypropyl-beta-cyclodextrin, carboxymethyl-beta-cyclodextrin and sulfobutylether-beta-cyclodextrin. More hydrophobic steroids were characterised by higher Ks values. Anionic beta-cyclodextrins showed high affinity for the steroids studied. Simple equipment and sufficient computing allowed recommendation of the method for express estimation of cyclodextrin's affinity for hydrophobic substrates.

Cyclodextrins↗

PubMed1996

FET-microbial sensor for xylose detection based on Gluconobacter oxydans cells.

A potentiometric biosensor for xylose was devised utilizing Gluconobacter oxydans whole cells. Immobilization methods based on physical adsorption were used for G. oxydans cells and extracellular pH changes resulting from xylose dehydrogenation were monitored by a field effect transistor (FET). The G. oxydans, FET-based sensor detected xylose at a lower limit of 0.5 mM. From 5.0 to 30 mM xylose, the response of the sensor was linear. Expectedly, output signals were significantly suppressed by buffer (Tris-HCl). Responses were essentially stable for at least four weeks of storage and showed only a slight loss of initial xylose sensitivity. Xylitol exerted an insignificant influence on the sensor's response to xylose. However, the response to glucose was 5 times higher in relation to that of xylose at the same concentration (1 mM). For xylose determinations in the presence of glucose, a two-step assay is discussed.

Acetobacteraceae↗