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Biomedical subjects

P S Nys

Publications and source records attributed to P S Nys.

At least 19 recordsLinked to original sources
PubMed2002

[Novel beta-lactam structures: design problems].

The methology of the development of new biologically active betalactams is proposed. One of the two ways proposed is specific modification which is peculiar to certain betalactam structure and involves introduction of substitutes changing particular physico-chemical properties of the natural or synthetic analogous. General guidelines for modification of the biologically active compounds are given. The space and depth of the necessary physico-chemical investigation are determined. The alternative way of the new biologically active compounds development is the principle of similarity. The distinctive feature of this approach is the use as building blocks of the substitutes already used in the well-known betalactam antibiotics and "implantation" of this substitutes into other (new) betalactam structures. The ways of the new betalactams synthesis including the methods of enzyme engineering are considered. The possibility to use enzyme engineering processes for production of not only new individual betalactams--hits, but also for synthesis of the groups of betalactams--leads, is shown. More than 6000 new betalactam structures were constructed on the base of the principle of similarity. At least 700 of this compounds demonstrates not only antimicrobial activity but other types of biological activity due to the implementation of additional pharmaceutical units other than betalactams. The constructed compounds are summarized in the tables, the request for the electronic version of the tables can be sent by the address: valan@orc.ru.

Anti-Infective Agents↗
PubMed1999

[Enzymatic synthesis of beta-lactam antibiotics. I. Cefazolin].

Production of cefazolin by acyl transfer enzymatic synthesis with immobilised cefazolin synthetase from Escherichia coli as a biocatalyst acting in accordance with the mechanism including formation of the acyl-enzyme complex was shown possible. The process kinetic parameters and the ratio of the maximum conversion of the key amino acid and the initial concentrations of the substrate and nucleophile were determined. Correlation of the calculated and experimental data on the cefazolin yield in the enzymatic synthesis was good. The main physico-chemical properties of the substrates and the reaction products i.e. dissociation constants and solubility were investigated. The complex of the physico-chemical studies makes it possible to design a highly efficient technological process for production of cefazolin including not only the stage of the enzymatic synthesis but also the stage of separation of the reaction mixture components.

Acylation↗
PubMed1999

[Enzymatic synthesis of beta-lactam antibiotics. II. Aminocephalosporins].

Enzymatic synthesis of cephalexin and cefaclor with the use of immobilized aminocephalosporin synthetase from Xanthomonas sp. as a biocatalyst was studied. The employment of a mathematical model based on the acyl-enzyme mechanism of the biocatalyst action was shown possible for the quantitative description of the antibiotic syntheses. A relationship providing determination of the complex of the physico-chemical investigations required for the enzymatic synthesis design was suggested. Kinetic and thermodynamic parameters of the processes were evaluated and the ratios of the maximum conversion of the key amino acids and the initial concentrations of the substrate and nucleophile were calculated. The regions of the model fit to the experimental data within a wide range of the substrate and nucleophile concentrations were defined. The technology for the enzymatic synthesis of aminocephalosporins exemplified by cephalexin and cefaclor was designed.

Acyltransferases↗
PubMed1995

[Kinetics of 7-aminocephalosporanic acid in aqueous solutions].

Stability of 7-aminocephalosporanic acid (7-ACA) and desacetyl-7-ACA in aqueous solutions at the pH value higher than 6 and wide ranges of the temperature was studied. The kinetic parameters of the hydrolysis of the ester link in the molecule of 7-ACA and the openings of the betalactam link in the molecules of 7-ACA and desacetyl-7-ACA were estimated. It was shown that all the destruction processes were describable by the 1st order equations. A procedure for the calculation of the velocity constants of the above mentioned three processes by changes in the concentration of 7-ACA and desacetyl-7-ACA in the solutions is described.

Biotransformation↗
PubMed1994

[Role of biocatalysis in the creation and improvement of production of beta-lactam antibiotics in Russia].

The paper presents the results of the studies carried out by the authors within 20 years on development of processes for production of beta-lactam antibiotics with using biocatalysis. The proposed general principles for the development of efficient biocatalytic technologies are discussed in regard to production of the key compounds and synthesis of beta-lactams. The paper includes 4 parts concerned with comparison of the biocatalytic and chemical processes for production of beta-lactam antibiotics, requirements to the quality of the biocatalysts used and criteria for estimation of the efficiency of the stage of the technological biocatalyst production. The criteria provided determination of the optimal biocatalyst for production of the key compounds in the synthesis of beta-lactams. A retrospective analysis of the biocatalytic processes for production of 6-amino-penicillanic acid is presented and the impact of the activity and the form of the biocatalyst on the process efficiency is substantiated. Various schemes of the enzymatic synthesis of beta-lactam antibiotics and the approaches to the improvement of the technological processes including those with the use of immobilized microbial cultures at the stage of the production of the initial biosynthetic antibiotics are described. The prospects for the improvement of the processes for production of drugs with the use of biocatalysis are indicated and the main trends of the research required for the large scale use of the immobilized enzymes, microbial cells, oligo-enzymatic and poly-enzymatic systems in transformation and synthesis of organic compounds are defined.

Anti-Bacterial Agents↗
PubMed1994

[Stability of various cephalosporins in solutions. Cefazolin, cefazedone, cefaclor].

The kinetics of splitting out the substitute at C3 in the molecule of beta-lactam antibiotics such as cefazolin, cefaclor, cefazedone and others as well as that of splitting out the chlorine atom in the side radical of the cefazedone molecule was studied within wide ranges of pH and temperature. The destruction processes for all the investigated compounds were shown to be described by the 1st order equations. The values of the activation energy, pre-exponential factors and reaction order by the hydrogen ions were measured. This provided the mathematical description of the destruction processes within wide ranges of pH and temperature. An unusual mechanism of synchronous splitting out the substitute at C3 and one of the chlorine atoms in the side radical of the cefazedone molecule was observed.

Anti-Infective Agents, Urinary↗
PubMed1993

Interrelated approach to optimization of biosynthesis and chemical isolation of biologically active substances: the production of penicillinamidase by Escherichia coli and peptidohydrolase by Xanthomonas sp.

The solution to the problem of optimizing conditions for the isolation of biologically active substances (BAS) from microbial cells should be based on investigations of the structural and functional characteristics of cultures. Models of two bacterial cultures, of Escherichia coli and a Xanthomonas species, producing enzymes the localization of which differ, is described. The isolation of membrane-bound penicillinamidase from E. coli was optimal in the 'preautolysis' period, when the components of the cytoplasm autolysed but the membranes remained intact. In contrast, the isolation of the cytoplasmic enzyme peptidohydrolase from Xanthomonas sp. was optimal during the period when the cell membranes markedly changed. Thus the physiological state of the cultures and the localization of the BAS within the cells are important determinants for optimization of the isolation process. It follows that all stages of a technological process for the production of BAS, i.e. biosynthesis, chemical isolation, etc., should be interrelated for a successful outcome.

Culture Media↗
PubMed1992

Coagulation autolysis in microorganisms and its relation to coagulase production.

The phenomenon of coagulation autolysis was observed in two model microorganisms, i.e., a bacterial culture and an imperfect fungus. It was characterized by impairment of the cell membranes, followed by condensation and dehydration of the cytoplasm and long-term preservation of the cells in the form of coagulated cytoplasm. In this respect, it was similar to coagulation necrosis of human tissues. The autolysis in the microorganisms was accompanied by increase of their coagulase activity, the substrate specificity of the enzyme rather broad. The coagulase activity of the microorganisms was detected during the culture period between the lag-phase and the exponential growth phase, i.e., the phase of their active growth. It served as a signal to induce biosynthesis of peptidohydrolase and cleavage of proteins. We believe that the phenomenon of coagulation autolysis in these microorganisms is rather typical and can be considered as an adaptative reaction, inducing a cascade of events from synthesis of coagulase to overproduction of peptidohydrolases with proteolytic activity.

Acremonium↗
PubMed1989

[Ways of developing the first and second generation biocatalysts for antibiotic production].

Methods for development of bioengineering systems of different types useful in synthesis and transformation of antibiotics are discussed. It was shown that in development of monoenzymatic biocatalysts on the basis of immobilized cells and in preparation of immobilized cultures producing secondary metabolites with enzymological engineering directed action on the cells could be provided which made it possible to establish highly efficient bioengineering systems. Various means for providing the directed action and method for estimation of the carrier-culture interation are proposed. The prospects of using the second generation biocatalysts in improvement of the processes for production of antibiotics are described.

Catalysis↗
PubMed1986

[Status and prospects in the use of biocatalysis in the synthesis of beta-lactam antibiotics].

The present world status of using biocatalysts for production of beta-lactam antibiotics and their semiproducts is analyzed and the biocatalytic and chemical methods for production of antibiotics are compared. The requirements to the quality of biocatalysts used in production of drugs are formulated and the criteria of the efficiency of biocatalytic production processes are presented. Interrelation between the requirements to the biocatalyst quality and the efficiency of the biocatalytic production processes is examined. The general principles of development of efficient enzymatic processes including biocatalytic processes in production of beta-lactam antibiotics as closed-loop and practically wasteless systems are discussed. The main advantages of the developed production processes are illustrated by an example of large-scale processes use in manufacturing of the basic products for synthesis of beta-lactam compounds.

Anti-Bacterial Agents↗
PubMed1984

[Penicillinase from B. licheniformis. Determination of the ionization constants of the enzymatic hydrolysis products of beta-lactam antibiotics].

The level of transformation of beta-lactam antibiotics hydrolysed by penicillinase from B. licheniformis on determination with the method of pH-metric titration with sodium hydrate solutions depended on the electrochemical nature of the products formed. The data on the study of the pH dependence of the penicillinase-catalysed hydrolysis of beta-lactam antibiotics were used for estimation of the ionization constants of the products of the enzymatic hydrolysis of the beta-lactam ring in the molecules of azlocillin, carfecillin, benzylpenicillin, cephalothin and 7-PADCA. Methods for quantitative determination of the compounds were developed. The methods are based on penicillinase-catalysed enzymatic hydrolysis and pH-metric titration of the products with sodium hydrate solutions at pH 7.0 with regard to their dissociation levels.

Anti-Bacterial Agents↗
PubMed1984

[Aminoacylase from Streptoverticillium microorganisms: stereo- and substrate specificity].

The stereo- and substrate specificity of a new aminoacylase from Streptoverticillium microorganisms was studied. The enzyme effectively hydrolyzes acetyl derivatives of aliphatic (methionine, leucine) and aromatic (phenylglycine, phenylalanine, tryptophan) amino acids. The L-enanthiomer of acetylphenylglycine is hydrolyzed by aminoacylase 8000 times more effectively than the D-enanthiomer. A procedure for determination of the enanthioselectivity of aminoacylases was elaborated. This procedure is designed for a detection and assessment of contaminations of the N-acetyl derivative of one enanthiomer by another enanthiomer of the amino acid, as well as of the degree of racemization of the substrate during hydrolysis of acetyl derivatives of D-amino acids.

Amidohydrolases↗
PubMed1982

[Extractive polarographic method of controlling the stereospecific hydrolysis of N-acylated derivatives of amino acid racemates].

The equilibrium distribution of acetyl-D-phenylglycine prepared with stereospecific hydrolysis of acetyl-D,L-phenylglycine (Ac-D,L-PhG) was studied in a two-phase system of benzyl alcohol-1N HCl solution. It was found that the distribution coefficient of Ac-D-PhG did not practically depend on its concentration in the aqueous phase. This means that Ac-D-PhG does not form associates in the organic phase. The studies provided development of an extraction polarimetric method for quantitative determination of Ac-D-PhG. The method implies extraction of Ac-D-PhG with benzyl alcohol from a strong acid medium (1N HCl solution), polarimetric determination of the equilibrium concentration of Ac-D-PhG in the organic phase and subsequent calculation of the initial concentration of Ac-D-PhG in the aqueous phase with regard to its distribution coefficient.

Acylation↗
PubMed1981

[E. coli penicillin amidase. Methods for estimating the close ionization constants of ionogenic groups of the enzyme complex with substrates containing free amino groups].

The possible use of various procedures for estimation of the ionization constants of the Michaelis complex by the pH dependence of the maximum enzymatic reaction rate is discussed. It is shown that the procedures described in the literature for estimation of the close ionization constants of the enzyme-substrate complexes have limitations and in some cases cannot be used. The paper presents the methods for estimation of the constants and means for quantitative description of the bell-shaped pH dependence of the kinetic and equilibrium parameters of the biocatalytic reaction. The equations recommended in the paper were used in analysis of the pH dependences of the maximum rate of the reactions during the enzymatic synthesis of cefalexin catalysed with immobilized penicillinamidase (IPA) (CE 3.5. 1.11). The ionization constants of the enzyme-substrate complexes of IPA were compared during hydrolysis and synthesis of the compounds acylated with phenylacetic and aminophenylacetic acids. The effect of the nature of the leaving substrate group and added nucleophilic gent on the electrochemical state of the Michaelis complex is discussed.

Amidohydrolases↗