Characteristics of the glucose isomerase from Streptomyces atratus

The molecular mass (Mr) of highly purified glucose isomerase fromStreptomyces atratus has been determined. The native glucose isomerase, which has affinity for xylose, consists of an oligomeric protein containing 1552 amino acid residues and formed of four subunits. The enzyme is stable in the range of temperatures from 40 to 80°C and at pH values of from 6.0 to 11.0.Institute of Microbiology, Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 833–837, November–December, 1991.     

Influence of metal ions on the activity and stability of the glucose isomerase from Streptomyces atratus

The influence of a number of bivalent metals on the activity ofStreptomyces atratus glucose isomerase has been studied. Mg²⁺ ions are activators and Co²⁺ ions are stabilizers of the glucose isomerase activity. The effective kinetic parameters for the action of the enzyme have been determined.Institute of Microbiology, Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 838–842, November–December, 1991.     

Immobilization ofStreptomyces atratus glucose isomerase on various supports

The immobilization ofStreptomycs atratus glucose isomerase has been achieved and the periods of half-life of the immobilized glucose isomerase have been determined on various supports, among which the most acceptable are cotton lint and polyurethane. The stability of the immobilized preparations has been demonstrated.Institute of Microbiology, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (82712) 41 71 29. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 670–672, September–October, 1994.     

Isolation,purification, and some physicochemical properties of glucose isomerase from Streptomyces atratus

A highly purified glucose isomerase with a specific activity 23.5 times greater than that of a homogenate of the mycelium has been obtained fromStreptomyces atratus by methods of homogenization from the freeze-dried biomass, heat treatment (70°C, 10 min), ion-exchange chromatography, and gel filtration. The yield of enzyme on the initial biomass was 51.8%. The molecular mass of the enzyme has been determined by various methods as 160 kDa but in the presence of sodium dodecyl sulfate in thin-layer PAG it amounts to 40 kDa.Institute of Microbiology, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 524–528, July–August, 1990.     

Enzymatic production of glucose syrups from cellulose-containing plant wastes

A method has been developed for obtaining glucose syrups from cellulose-containing plant wastes under the action of a complex of cellulases from a hybrid strain of fungus. Purified glucose syrups containing 19–20 mg/ml of reducing sugars have been obtained.Institute of Microbiology, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 41 71 29. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 358–361, May–June, 1997.     

Preparation and properties of glucose isomerase immobilized on Indion 48-R

Partially purified glucose isomerase fromStreptomyces thermonitrificans when coupled to glutaraldehyde-activated Indion 48-R, retained 30–40% activity of the soluble enzyme. However, an approximately twofold increase in the activity could be achieved by binding the enzyme in the presence of glucose. Binding the enzyme to matrices presaturated with either glucose or fructose and influence of lysine modification on the activity of the soluble enzyme revealed that the comparatively low activity observed in case of the enzyme bound in the absence of substrate is the result of the nonspecific binding of either substrate or product to the matrix. Immobilization did not affect the pH and temperature optima of the enzyme, but it lowered the temperature stability. Immobilization resulted in a marginal increase in theK _m and a threefold decrease in theV _max . Substrate concentrations as high as 36% glucose could be converted to 18.5% fructose in 5 h, at pH 7.0 and 70‡C. The bound enzyme, however, showed inferior stability to repeated use and lost approx 40% of its initial activity after five cycles of use. Indion 48-R bound glucose isomerase could be stored, in wet state, for 30 d without any apparent loss in its initial activity.     

Production of glucose-fructose syrups from fermentative hydrolysates of plant wastes

A method has been developed for obtaining glucose—fructose syrups by the hydrolysis of plant wastes under the action of a complex of cellulases from a hybrid strain of a fungus, followed by isomerization of part of the glucose to fructose by immobilized streptomycete glucose isomerase. The conditions for raising the degree of isomerization of the glucose and the period of half-inactivation of the immobilized glucose isomerase have been optimized, with a simultaneous cheapening of the process. Plant raw materials that have been used for obtaining glucose–fructose syrups are maize cobs, wheat or rice straw, and reeds. Isomerization has been achieved by streptomycete cells immobilized on cotton lint. Institute of Microbiology of the Academy of Sciences, Republic of Uzbekistan, Tashkent, fax (3712) 41 71 29. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 449–451, July–August, 1998.     

Study of the structure of the lectins ofDatura innoxia seeds. III. Resistance of the lectins to the action of various proteases

The capacity of the lectins ofDatura innoxia for being digested by proteases with various specificities and pH optima has been studied. Under the conditions of limited proteolysis the hemagglutinating activity did not decrease, and the degree of hydrolysis determined from the reaction with trinitrobenzenesulfonic acid was close to zero.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 93–95, January–February, 1996. Original article submitted July 3, 1995.     

Characteristics of the glucose isomerase from Streptomyces atratus

The molecular mass (Mr) of highly purified glucose isomerase fromStreptomyces atratus has been determined. The native glucose isomerase, which has affinity for xylose, consists of an oligomeric protein containing 1552 amino acid residues and formed of four subunits. The enzyme is stable in the range of temperatures from 40 to 80°C and at pH values of from 6.0 to 11.0.     

Influence of metal ions on the activity and stability of the glucose isomerase from Streptomyces atratus

The influence of a number of bivalent metals on the activity ofStreptomyces atratus glucose isomerase has been studied. Mg²⁺ ions are activators and Co²⁺ ions are stabilizers of the glucose isomerase activity. The effective kinetic parameters for the action of the enzyme have been determined.     

Carbon-silica composite matrices for preparing heterogeneous biocatalysts with glucose isomerase activity

Comparative studies have been carried out on the preparation of carbon-silica composite matrices for heterogeneous biocatalysts with glucose isomerase activity. Carbon nanotubes and nanofibers have been included inside SiO₂ xerogel. The enzymatic activity and operating stability of the biocatalysts have been investigated. Bacterial cells of a recombinant glucose isomerase producer strain have been used as the enzymatically active component of the biocatalysts. The steady-state activity of the biocatalysts subjected to “dry” cross linking with a glutaraldehyde solution (0.1–1%) is 1.5 times higher than the activity of the biocatalysts containing no nanocarbon. The initial and steady-state glucose-isomerase activities of the biocatalysts at 70°C are ∼520–540 and ∼150–160 μmol min⁻¹ g⁻¹, respectively. The half-inactivation time of the biocatalysts under continuous monosaccharide (glucose, fructose) isomerization conditions is up to ∼1500 h.     

Immobilization ofStreptomyces atratus glucose isomerase on various supports

The immobilization ofStreptomycs atratus glucose isomerase has been achieved and the periods of half-life of the immobilized glucose isomerase have been determined on various supports, among which the most acceptable are cotton lint and polyurethane. The stability of the immobilized preparations has been demonstrated.     

Pectin substances ofAmaranthus cruentus

Pectin substances have been isolated from the epigeal pan of love-lies-bleeding,Amaranthus cruentus (A. caudatus), and have been characterized. The presence in them of galacturonic acid, galactose, rhamnose, xylose, arabinose, fructose, and glucose residues has been established. The titrimetric indices of the substances isolated have been determined and they have been studied by IR spectroscopy.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 7–9, January–February, 1996. Original article submitted August 14, 1995.     

Glucose biosensor based on glucose oxidase immobilized in sol–gel chitosan/silica hybrid composite film on Prussian blue modified glass carbon electrode

An improved amperometric glucose biosensor based on glucose oxidase immobilized in sol–gel chitosan/silica hybrid composite film, which was prepared from chitosan (CS) and methyltrimethoxysilane (MTOS), on the surface of Prussian blue (PB)-modified glass carbon electrode was developed. The film was characterized by FT-IR. Effects of some experimental variables such as ratio of CS to silica, buffer pH, temperature, and applied potential on the current response of the biosensor were investigated. The biosensor fabricated under optimal conditions had a linear response to glucose over the range 5.0×10^–5 to 2.6×10^–2 M with a correlation coefficient of 0.9948 and a detection limit of 8.0×10^–6 M based on S/N =3. The biosensor had a fast response time of less than 10 s, a high sensitivity of 420 nA mM^–1, a long-term stability of over 60 days, and a good selectivity. The apparent Michaelis–Menten constant K_m was found to be 3.2×10^–3 M. The activation energy for enzymatic reaction was calculated to be 21.9 kJ mol^–1. This method has been used to determine the glucose concentration in real human blood samples.     

Purification and characteristics of the endo-1,4-β--glucanase formed by the hybrid fungusTrichoderma harzianum-G-1

An endo-1, 4--glucanase consisting of a low-molecular-mass enzyme with a molecular mass of 19,862 Da has been isolated for the culture liquid of the hybrid fungusTrichoderma harzianum-G-1.Institute of Microbiology of the Academy of Sciences, Republic of Uzbekistan, Tashkent, fax (3712) 41 71 29. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 908–911, November–December, 1996. Original article submitted September 11, 1996.     

Detection and separation of two forms of cotton-plant pyrophosphatase

Two pyrophosphatase isoenzymes with identical molecular weights but differing in the pH optima of their action and also in their senstivity to some bivalent metal ions have been isolated from extracts of the cotyledons of three-day cotton-plant shoots by gel filtration and ion-exchange chromatography.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 375–378, May–June, 1985.     

Berberis alkaloids. XXXVII. Investigation of the alkaloids ofB. oblongata andB. integerrima. Crystal structure of 8-trichloromethyldihydroberberine

Two species of Berberis have yielded 10 isoquinoline alkaloids. In addition to known bases, two artifacts have been isolated — 8-trichloromethyldihydroberberine (I) and 8-trichloromethyldihydropalmatine. An x-ray structural analysis has been made of (1).Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 889–893, November–December, 1996. Original article submitted April 15, 1996.     

Phlomoside D — an iridoid glycoside fromPhlomis regelii

A new iridoid – phlomoside D- has been isolated from the epigeal organs ofPhlomis regelii (M. Pop). Its structure has been established on the basis of chemical transformations and spectral characteristics.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 551–553, July–August, 1996. Original article submitted February 5, 1996.     

Effect of pH on simultaneous saccharification and isomerization by glucoamylase and glucose isomerase

pH and temperature play critical roles in multistep enzymatic conversions. In such conversions, the optimal pH for individual steps differs greatly. In this article, we describe the production of glucoamylase (from Aspergillus oryzae MTCC152 in solid-state fermentation) and glucose isomerase (from Streptomyces griseus NCIM2020 in submerged fermentation), used in industries for producing high-fructose syrup. Optimum pH for glucoamylase was found to be 5.0. For glucose isomerase, the optimum pH ranged between 7.0 and 8.5, depending on the type of buffer used. Optimum temperature for glucoamylase and glucose isomerase was 50 and 60°C, respectively. When both the enzymatic conversions were performed simultaneously at a compromised pH of 6.5, both the enzymes showed lowered activity. We also studied the kinetics at different pHs, which allows the two-step reaction to take place simultaneously. This was done by separating two steps by a thin layer of urease. Ammonia generated by the hydrolysis of urea consumed the hydrogen ions, thereby allowing optimal activity of glucose isomerase at an acidic pH of 5.0.     

Isolation,purification, and study of some properties of the extracellular lignin peroxidases of the wood-destroying fungusPleurotus ostreatus

Abstact Two bands with lignin peroxidase activity have been detected by isoelectric focusing in a total enzyme preparation obtained from a 15-day filtrate of the culture liquid of the fungusPleurotus ostreatus by fractionation with ammonium sulfate. Two homogeneous forms of the enzymes — LGP-I and LGP-II — have been obtained by gel filtration on Sephadex G-100, ion-exchange chromatography on DEAF-Toyopearl 650 M gel, and rechromatography on Sephadex G-75, and also by electrophoresis in PAAG. The specific activities of the purified lignin peroxidases LGP-I and LGP-H amounted to 36.5 and 54.3 units/mg, their degrees of purification being 8.7 and 12.9, respectively. The molecular masses of LGP-I and LGP-II, determined by electrophoresis in PAAG in the presence of Na-DS and by gel filtration on TSK HW–65 gel were 42–44 and 61–63 kDa. The isoelectric points of LGP-I and LGP-II were 3.4 and 4.1, their pH optima 2.7 and 3.4, and the, temperatures of their optimum enzymatic action 28 and 34°C, respectively. The isoenzymes differed from one another substantially with respect to pH stability and resistance to heat. The values of K_M determined from the rates of hydrolysis of the substrate by the enzymes in the presence of H₂O₂ at pH 3.7 were 0.09 mM for LGP-I and 0.07 mM for LGP-II. The values of K_M with respect to veratryl alcohol, determined by the Lineweaver—Burk method, were 0.117 mM for LGP-II and 0.132 mM for LGP-II.Institute of Microbiology, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 41 71 29. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 394–402, May–June, 1996. Original article submitted November 11, 1994.