[Effect of low-intensity 900 MHz frequency electromagnetic radiation on rat liver and blood serum enzyme activities].

The comparative analysis of the rat liver and blood serum creatine kinase, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and purine nucleoside phosphorylase post-radiation activity levels after a total two-hour long single and fractional exposure of the animals to low-intensity 900 MHz frequency electromagnetic field showed that the most sensitive enzymes to the both schedules of radiation are the liver creatine kinase, as well as the blood serum creatine kinase and alkaline phosphatase. According to the comparative analysis of the dynamics of changes in the activity level of the liver and blood serum creatine kinase, alanine aminotransferase, aspartate aminotransferase and purine nucleoside phosphorylase, both single and fractional radiation schedules do not affect the permeability of a hepatocyte cell membrane, but rather cause changes in their energetic metabolism. The correlation analysis of the post-radiation activity level changes of the investigated enzymes did not reveal a clear relationship between them. The dynamics of post-radiation changes in the activity of investigated enzyme levels following a single and short-term fractional schedules of radiation did not differ essentially.

[Influence of ionizing radiation on enzymatic activity and state of nucleus-nucleolar apparatus in rat hepatocytes].

The effects of a single exposure of rats to the whole-body roentgen irradiation at the doses of 3.5 Gy and 4.5 Gy on the activity of creatine kinase, purine nucleoside phosphorylase, alanine aminotransferase, aspartate aminotransferase, as well as on the state of the nuclear-nucleolar apparatus in rat hepatocytes on the 6th and 13th days after radiation exposure have been studied. Irradiation at the above doses induced changes in the levels of enzymatic activity of different values and different directions within the same time periods, as well as oscillating changes in this type of enzymatic activity over time. This demonstrates various radiosensitivity and adaptation abilities of these enzymatic activities. The changes in the enzymatic activity significantly correspond to the changes in the morphometric indices of nuclear-nucleolar apparatus of hepatocytes, as well as the distribution of hepatocytes within the ploidy classes: in particular, stabilization of the enzymatic activity on the 13th day after irradiation correlates with the increased transcriptional activity, which is detectable through the increased number of nucleoli per nucleus and the expanded space of a hepatocyte nucleus. The compensation mechanisms are likely to be targeted at the changes in the functional activity of surviving hepatocytes, rather than at the replacement of the damaged cells by the new ones.

[Production of fructooligosaccharide syrup from sucrose in combination with palatinose and trehalose].

The fructofuranosidases (EC 3.2.1.26) of Aspergillus niger St-0018 and A. foetidus St-0194 were used to produce fructooligosaccharides (FOS) under periodic and continuous conditions. The incorporation of cells into calcium alginate gel gave the most efficient immobilized biocatalysts. The feasibility of transforming residual sucrose into palatinose and trehalulose using isomaltulose synthase (EC 5.4.99.11) was demonstrated.

[Transglycosylation of L-ascorbic acid].

Cyclodextrin glucanotransferases (CGTase, EC 2.4.1.19) produced by mesophilic, thermophilic, and halophilic bacilli, as well as maltase (EC 3.2.1.20) produced by various strains of Saccharomyces cerevisiae have been applied for transglycosylation of L-ascorbic acid using starch, maltodextrin, gamma-cyclodextrin, and maltose as donors of glucosyl residue. The CGTases produced by thermophilic strains are the most efficient. The degree of transglucosylation is more than 60%.

[Antitumor activity of Ca-double-stranded RNA from sodium nucleinate]. / Protivoopukholevaia aktivnost' Ca-dvukhspiral'noi RNK iz nukleinata natriia.

Ca-dsRNA introduced in the concentration of 5 micrograms per mouse 24 hours before the MG22a mouse hepatoma transplantation causes the 70% inhibition of the hepatoma growth. The sodium nucleinate used in the considerably higher concentration had a less effect. The sodium form of dsRNA also had a less antitumour effect comparing with its calcium form. The calcium form of dsRNA proves to be relatively stable and physiologically active form of dsRNA during its parenteral administration.

[Creatine kinase from rabbit skeletal muscles: formation of O-acyltyrosine as a result of the activation of the carboxylic group of the enzyme active site by affinity reagents, nucleotide imidazolides]. / Kreatinkinaza iz skeletnykh myshts krolika: obrazovanie O-atsiltirozina v rezul'tate aktivatsii karboksil'noi gruppy aktivnogo tsentra fermenta pod deistviem affinnykh reagentov-- imidazolidov nukleotidov.

Creatine kinase from skeletal muscle (EC 2.7.3.2) was inactivated by means of imidazolides of AMP, ADP, ATP. Rates of the inactivation of the enzyme's M- and M'-subunits differ 50-100 fold and decrease in the presence of ADP and ATP. Differential spectrum of the native and modified enzymes corresponds to the spectrum of N,O-diacetyltyrosine. Kinetic curves of hydroxylamine-dependent destruction of N,O-diacetyltyrosine and of alteration of differential spectrum of the modified and native enzymes essentially coincide. The enzyme's inactivation appears to be caused mainly by the formation of a bond between nucleotide imidazolides activated carboxyl group of the active centre and OH-group of Tyr residue arranged in the close proximity. The stoichiometry of acyltyrosine formation is evaluated as 2.1 +/- 0.2 mole per mole of the functional dimer. Along with formation of ester bond between amino acid residues, a covalent attachment of 0.03-0.06 mole of [14C]nucleotides per mole of enzyme is observed. As the data of acid hydrolysis show, Im-ATP and Im-AMP block epsilon-amino group of Lys and guanidine group of Arg, respectively. Reasons of the multiple modification of creatine kinase by affinity reagents are discussed. The results obtained and literature data are summarised in the hypothetical scheme of disposition of various amino acid residues in the active centre of creatine kinase.

[Inhibition of activity of purine nucleoside phosphorylase with N9- and N7-(beta-D-glucofuranuronosyl)purines and 8-substituted N9-(beta-D-ribofuranosyl)purines)]. / Ingibirovanie aktivnosti purinnukleozidfosforilazy N9- i N7-(beta-D-gliukofuranuronozil)puranami i 8-zameshchennymi N9-(beta-D-ribofuranozil)purinami.

In an effort to develop more potent inhibitors of purine nucleoside phosphorylase (PNP, EC 2.4.2.1) as immunosuppressive and anticancer chemotherapeutic agents, the affinity of the electrophoretically homogeneous enzyme from rabbit kidney for sixteen N9- and N7-beta-D-glucofuranuronosides and for C8-substituted beta-D-ribofuranosyl purines was determined. In all cases N7-substituted analogues of hypoxanthine and guanine were twice more active inhibitors of PNP than N9-substituted compounds. No effective inhibitors were found among the C8-substituted analogues, apparently due to the bulky C8-groups hindering rotation around the glycosidic bond and thus preventing optimal binding with the enzyme.

[Extrachromosomal DNA spectrum of Bacillus thuringiensis Berliner and Bacillus sphaericus Meyer et Neide]. / Issledovanie spektra ékstrakhromosomal'nykh DNK Bacillus thuringiensis Berliner i Bacillus sphaericus Meyer et Neide.

Analysis of the pattern of extrachromosomal DNA in different cultures of Bacillus thuringiensis and Bacillus sphaericus demonstrated a higher content of extrachromosomal DNA in B. thuringiensis than in B. sphaericus. The quantity and approximate molecular weights of the plasmids were determined. The assumption that the plasmid DNA content in B. thuringiensis strains is higher than in the other representatives of the genus Bacillus was confirmed.

[Regulatory mutants for the synthesis of a 2d purine nucleoside phosphorylase in Escherichia coli K-12. I. Synthesis inducers and the substrate specificity of purine nucleoside phosphorylase in pndR mutants]. / Reguliatornye mutanty po sintezu vtoroi purinnukleozidfosforilazy u Escherichia coli K-12. Soobshchenie I. Induktory sinteza i substratnaia spetsifichnost' purinnukleozidfosforilazy u mutantov pndR.

Restoration of the ability to catabolise the purine nucleosides in phenotypic revertants of Escherichia coli K-12 mutants defective in deoD encoded purine nucleoside phosphorylase (PNPase 1) is the result of regulatory pndR mutations for synthesis of a second purine nucleoside phosphorylase (PNPase 2). In pndR+ strains synthesis of PNPase 2 is induced by xanthosine; in pndR mutants catabolising all purine nucleosides synthesis of this enzyme is constitutive; in other pndR mutants only catabolising some of purine nucleosides, this catabolisible nucleosides, namely, deoxyinosine, deoxyadenosine as well as, in some cases, inosine and adenosine, act as inducers of PNPase 2 synthesis. In some pndR mutants with inducible PNPase 2, xanthosine is a stronger inducer, in others it is weaker, in comparison with pndR+ strains. In bacterial cells PNPase 2 catalyses the phosphorolytic cleavage of adenosine, inosine, deoxyinosine, guanosine, deoxyguanosine and xanthosine, though in crude extracts adenosine and deoxyadenosine phosphorylase activities of the enzyme are not expressed.

[Escherichia coli K-12 mutants assimilating adenine via a new metabolic pathway]. / Mutanty Escherichia coli K-12, usvaivaiushchie adenin po novomu metabolicheskomu puti.

Two pathways of adenine utilization are only known in Escherichia coli K-12: the conversion to adenosine monophosphate by adenine phosphoribosyltransferase (apt gene) and ribosylation to adenine nucleosides by purine nucleoside phosphorylase (deoD gene). The purine auxotrophs defective in synthesis of inosine monophosphate de novo (pur) and carrying apt and deoD mutations cannot satisfy their purine requirements by exogenously supplied adenine or adenosine. We have selected spontaneously secondary-site revertants (designated adu) of pur apt deoD mutants, by plating on adenine or adenosine as the sole purine source. The adu mutations frequency was 6-10(-7). The phenotypical suppression of adenine phosphoribosyltransferase and purine nucleoside phosphorylase deficiency by adu mutations is neither the consequence of apt + or deoD + reversions nor the result of appearance in mutant cells of any activity converting adenine to adenosine monophosphate or adenosine. Adenine utilization in adu mutants is not caused by constitutive synthesis or genetic modification of the substrate specificity of adenosine deaminase (add gene). The direct deamination of adenine to give hypoxanthine in extracts of adu2 mutant has been shown. The data obtained suggest the possibility of a new adenine deaminase activity to appear in E. coli by means of single mutations.

[Purification and various properties of creatine kinase MM isoenzyme from the human heart muscle]. / Ochistka i nekotorye svoistva izofermenta MM kreatinkinazy iz serdechnoi myshtsy cheloveka.

Homogeneous preparation of creatine kinase MM isoenzyme was isolated from human heart muscle using affinity chromatography on Sepharose containing immobilized Cibachron blue F3G-A. The enzyme was active at a wide range of pH 5.0-8.0 exhibiting maximal activity at pH 6.0-6.7. Dependence of the initial rate of creatine kinase reaction on the ADP concentration at pH 6.6 in presence or absence of Mg2+ did not follow the Michaelis-Menten kinetics, while hyperbolic dependence was found at pH 7.6 and pH 5.2. In presence of Mg2+ Km value for ADP at pH 7.6 and pH 5.2 was decreased 4-fold and 1.3-fold, respectively, whereas Vmax was increased 2-fold and 2.5-fold, respectively. Besides, Km value for Mg2+-ADP at pH 7.6 was 3-fold higher than at pH 5.2, while these Km values were similar for ADP. The data obtained suggest that in human heart functional dissimilarity of creatine kinase MM subunits appears to occur, which is of importance in regulation of transphosphorylation.

[Creatine kinase of the human placenta]. / Kreatinkinaza platsenty cheloveka.

Studies have been made of the activity and isoenzymic spectrum of creatine kinase from human placenta at various stages of its development. Pure preparation of the enzyme was obtained which exhibited low specific activity and intermediate (between MB and BB isoenzymes of creatine kinase) electrophoretic mobility. Some of the properties of this enzyme are described and compared to those of creatine kinase from the brain of rabbits.

[Role of individual phospholipids in the functional activity of human myocardial creatine kinase]. / Rol' individual'nykh fosfolipidov v funktsional'noi aktivnosti kreatinkinazy serdechnoi myshtsy cheloveka.

Regulating effect of individual phospholipids on the activity of creatine kinase MM from human myocardium was studied. Cardiolipin, phosphatidic acid, phosphatidyl serine and phosphatidyl choline (dipalmitoyl) stimulated the enzymatic activity, while phosphatidyl inositol and lysophosphatidyl choline inhibited the creatine kinase MM activity by 80-100%. When mechanisms of the phospholipids inhibitory effects were studied, mixed type of inhibition was detected in the presence of phosphatidyl inositol and non-competitive type--in presence of lysophosphatidyl choline if guanidine was used as a substrate. Phosphatidyl inositol and lysophosphatidyl choline inhibited creatine kinase MM by the uncompetitive type if ADP was used as a substrate.

[Purine nucleoside phosphorylase].

Purine nucleoside phosphorylase (PNP) is one of the most important enzymes of the purine metabolism, wich promotes the recycling of purine bases. Nowadays is the actual to search for effective inhibitors of this enzyme which is necessary for creation T-cell immunodeficient status of the organism in the organs and tissues transplantation, and chemotherapy of a number pathologies as well. For their successful practical application necessary to conduct in-depth and comprehensive study of the enzyme, namely a structure, functions, and an affinity of the reaction mechanism. In the review the contemporary achievements in the study of PNP from various biological objects are presented. New data describing the structure of PNP are summarised and analysed. The physiological role of the enzyme is discussed. The enzyme basic reaction mechanisms and actions are considered. The studies on enzyme physicochemical, kinetic, and catalytic research are presented.

[Some inhibitors of purine nucleoside phosphorylase].

Purine nucleoside phosphorylase (PNP) catalyzes reversible phosphorolysis of purine deoxy- and ribonucleosides with formation (d)Rib-1-P and corresponding bases. PNP plays a leading role in the cell metabolism of nucleosides and nucleotides, as well as in maintaining the immune status of an organism. The major aim of the majority of studies on the PNP is the detection of highly effective inhibitors of this enzyme, derivatives ofpurine nucleosides used in medicine as immunosuppressors, which are essential for creating selective T-cell immunodeficiency in a human body for organ and tissue transplantation. The present work is devoted to the study of the effects of some synthetic derivatives of purine nucleosides on activity of highly purified PNP from rabbit spleen and also from human healthy and tumor tissues of lung and kidneys. Purine nucleoside analogues modified at various positions of both the heterocyclic base and carbohydrate residues have been investigated. Several compounds, including 8-mercapto-acyclovir, 8-bromo-9-(3,4-hydroxy-butyl)guanine, which demonstrated potent PNP inhibition, could be offered for subsequent study as immunosuppressors during organ and tissue transplantation.