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Biomedical subjects

N A Rodionova

Publications and source records attributed to N A Rodionova.

At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

[Purification and characteristic of endo-(1--4)-beta-xylanase from Geotrichum candidum 3C].

A method of purification of endo-(1-->4)-beta-xylanase (endoxylanase; EC 3.2.1.8) from the culture liquid of Geotrichum candidum 3C, grown for three days, is described. The enzyme purified 23-fold had a specific activity of 32.6 U per mg protein (yield, 14.4%). Endoxylanase was shown to be homogeneous by SDS-PAGE (molecular weight, 60 to 67 kDa). With carboxymethyl xylan as substrate, the optimum activity (determined viscosimetrically) was recorded at pH 4.0 (pI 3.4). The enzyme retained stability at pH 3.0-4.5 and 30-45 degrees C for 1 h. With xylan from beach wood, the hydrolytic activity of the enzyme (ability to saccharify the substrate) was maximum at 50 degrees C. In 72 h of exposure to 0.2 mg/ml endoxylanase, the extent of saccharification of xylans from birch wood, rye grain, and wheat straw amounted to 10, 12, and 7.7%, respectively. At 0.4 mg/ml, the extent of saccharification of birch wood xylan was as high as 20%. In the case of birch wood xylan, the initial hydrolysis products were xylooligosaccharides with degrees of polymerization in excess of four; the end products were represented by xylobiose, xylotriose, xylose, and acid xylooligosaccharides.

Endo-1,4-beta Xylanases↗
PubMedDate not supplied

[Formation of an extracellular system of enzymes during growth of Geotrichum candidum 3C on cell walls isolated from cereal grain capsules].

The activities of extracellular systems of hemicellulases, pectinases, and cellulases was studied during a 72-h cultivation of Geotrichum candidum 3C. The culture was grown on a medium containing 3% cell walls isolated from wheat grain capsules, which served as the sole carbon source. Enzymes catalyzing the degradation of pectin substances (beet pectin, alpha-L-arabinan, and 1,4-beta-D-galactan), as well as beta-D-galactosidase and alpha-L-arabinofuranosidase involved in their hydrolysis, were formed first (4 h after the beginning of cultivation). Enzymes hydrolyzing 4-O-methyl-alpha-D-glucurono-beta-D-xylan and sodium carboxymethyl xylan were also found in the culture liquid after 4 h of fungal growth. The contents of pectin-degrading and xylanolytic enzymes reached their maximum levels after 52-56 and 72 h of growth, respectively. Cellulolytic enzymes were detected after 8-28 h of cultivation. Enzymes degrading alpha-D-galacto-beta-D-mannan were found 24 h after the beginning of growth; their content was maximum after 72 h of cultivation.

Cell Wall↗
PubMedDate not supplied

[Formation of xylitol in Candida guilliermondii 2581 culture].

The yeast strain Candida guilliermondii 2581 was chosen for its ability to produce xylitol in media with high concentrations of xylose. The rate of xylitol production at a xylose concentration of 150 g/l is 1.25 g/l per h; the concentration of xylitol after three days of cultivation is 90 g/l; and the relative xylitol yield is 0.6 g per g substrate consumed. The growth conditions were found that resulted in the maximum relative xylitol yield with complete consumption of the sugar: xylose concentration, 150 g/l; pH 6.0; and shaking at 60 rpm. It was shown that the growth under conditions of limited aeration favors the reduction of xylose.

Candida↗
PubMedDate not supplied

[Ethylene-induced activation of xylanase in adventitious roots of maize as a response to the stress effect of root submersion].

Submersion of roots of ten-day-old maize (Zea mays L.) seedlings was accompanied by a decrease in pO2 and an increase in pCO2 of the medium adjacent to roots. These changes stimulated ethylene evolution in intact plants. Enhanced biosynthesis of ethylene was accompanied by xylanase activation in adventitious roots. As a result, an enhanced formation of aerenchyma was observed in the cortex of adventitious roots. Therefore, these processes resulted in the development of a ventilation system by which O2 can reach the root system exposed to hypoxia. The volume of aerenchyma was assessed by the volume of gas cavities (porosity). In contrast to the main root, the growth of adventitious roots was not inhibited under these conditions. Enlargement of the stem base and increase in the number of aerenchymatous adventitious roots facilitated the oxygen supply to submerged organs of plants.

Adaptation, Physiological↗
PubMedDate not supplied

[Use of the enzyme preparation cellocandin from Geotrichum candidum 3C-106 for difibering of waste paper and dessication of cellulose suspension].

The effect of cellocandin, an enzymatic preparation from Getrichum candidum 3C-106 with cellulolytic and xylanolytic activities, on defibring of waste paper and acceleration of desiccation of paper pulp was studied. It was shown that cellocandin accelerated defibring of waste paper to cellulose fibers and desiccation of cellulose suspension.

Biodegradation, Environmental↗
PubMedDate not supplied

[Isolation of endo-1,4-beta-xylanase from Geotrichum candidum 3C with various ability of sorption on an insoluble substrate].

Culture liquid from Geotrichum candidum 3C was shown to contain three endoxylanase types: endoxylanase I that binds to cellulose, endoxylanase II that sorbs to insoluble xylan, and endoxylanase III that cannot sorb to dissoluble substrate. The catalytic and substrate-binding domains of endoxylanase II were isolated.

Electrophoresis, Polyacrylamide Gel↗
PubMedDate not supplied

[An immunoregulatory effect of endoglucanase preparations on plant resistance to fungal infections].

Effects of enzymatic preparations--pectomacerin, hemicellulase, and Trichoderma viride 13/10 cellulase--on the plant immunological status were studied by examples of the pathosystems carrot root-white rot agent (Sclerotinia libertiana) and carrot root-black rot agent (Rhizopus nigricans). It was demonstrated that these preparations reduced the damage of infections, namely, decreased the permeability of cell membranes in infected tissue and stimulated its defense responses, which manifested itself in a stable elevation in the content of phenolic compounds and formation of tissue protective barriers.

Adjuvants, Immunologic↗
PubMedDate not supplied

[Staged equilibrium of carbonic anhydrase unfolding in strong denaturants].

It has been shown by 1H-NMR, circular dichroism, fluorescence and viscometry techniques that equilibrium unfolding of carbonic anhydrase B (a one-domain globular protein) in urea guanidine hydrochloride consists of two sequential stages. The first stage is connected with a decrease of intramolecular interactions, stabilizing the rigid tertiary structure and with the increase of mobility of aliphatic side chain groups. At the second stage the decrease of protein secondary structure and hydrophobic interactions take place as well as the increase of mobility of massive aromatic side chain groups.

Carbonic Anhydrases↗
PubMedDate not supplied

[Properties of the exo-1,4-beta-xylosidase of Aspergillus niger 15].

Properties of exo-1,4-beta-xylosidase from the fungus Aspergillus niger 15 were investigated. The enzyme was homogeneous during gel filtration, electrophoresis in polyacrylamide gel in the presence and absence of Na dodecyl sulfate, ultracentrifugation and isoelectric focusing. The enzyme had a temperature optimum at 70 degrees, pH optimum 3.8-4.0 for p-nitrophenyl-beta-D-xylopyranoside (p-NPX), was stable at pH 3-8, retained its 100% activity for 1 hour at 50 degrees and 42% activity at 60 degrees. Km was 0.23 mM for p-NPX and 0.67 mM for xylobiose. Xylose was a competitive inhibitor of exo-1,4-beta-xylodidase with Ki = 2.9 mM. The enzyme showed a transglycosilase activity. The aminoacid analysis of exo-1,4-beta-xylosidase showed that the enzyme molecule contained predominantly dicarboxylic and hydrophobic amino acids as well as serine. The enzyme contained no carbohydrates. Its activity was inhibited by p-chloromercury benzoate.

Amino Acids↗
PubMedDate not supplied

[Transglycosylation reactions catalyzed by Aspergillus niger 15 beta-xylosidase].

The products of transglycosylation formed as a result of action of beta-xylosidase from Aspergillus niger 15 on p-nitrophenyl-beta-D-glucopyranoside and p-nitrophenyl-beta-D-xylopyranoside were studied by means of chromatography on sephadexes. They are formed at the substrate concentration of 10--100 mM with the amount 7--10 times less than that of hydrolysis products. Peculiarities of chromatography of substrates, products of transglycosylation and p-nitrophenol on Sephadexes G-15 and G-25 were analysed.

Aspergillus niger↗
PubMedDate not supplied

beta-Xylosidase from Aspergillus niger 15: purification and properties.

Homogeneous (as judged by data from gel filtration, ultracentrifugation, polyacrylamide gel electrophoresis with and without sodium dodecyl sulfate (SDS), and isoelectric focusing) beta-xylosidase showing beta-D-xylosidase, beta-D-glucosidase, beta-D-galactosidase, and alpha-L-arabinosidase activities has been isolated from the hemicellulase preparation of the microscopic fungus Aspergillus niger 15 by ethanol fractionation and chromatography on Sephadex G-50, cellulose DE-52, and Sephadexes SP C-50 and G-200. The specific activity of the enzyme toward p-nitrophenyl-beta-D-xylopyranoside (p-NPX) increased 199-fold and was equal to 35.2 units/mg of protein; the activity yield was 43%. The sedimentation coefficient was equal to 10.6 S, and the molecular weight was 253,000 according to the gel filtration data and 122,000 according to the data from SDS electrophoresis. The isoelectric point was at pH 4.9. An amino acid analysis has shown that dicarboxylic and hydrophobic amino acids prevail in the enzyme. beta-Xylosidase had no carbohydrate component, and p-chloromercuribenzoate inhibited its activity. The temperature optimum of beta-xylosidase activity toward p-NPX was at 70 degrees C, and the pH optimum was 3.8-4.0. The enzyme was stable at pH 3 to 8 and did not lose its activity for 1 h at temperatures up to 50 degrees C. D-Xylose was found to be a competitive inhibitor of the beta-D-xylosidase activity of the enzyme with Ki = 2.9 mM. beta-Xylosidase showed transglycosylase activity.

Amino Acids↗