Kinetic aspects of reactions in homogeneous multienzyme systems under nonsteady state conditions were investigated. An analysis of formal-kinetic relationships, describing the time course of system was conducted with a bienzyme system. Presteady state kinetics of processes in lineal multienzyme systems was investigated. Relax-kinetics methods were applied for the analysis of processes in lineal sequences. Methods of determination of number of stages initial substrate transformations and of number of enzymes were developed as well as methods for the analysis of sequences of intermediates in reaction pathway. Methods of determination of Vmax and Kmax for each individual enzyme are considered.

Enzymes↗

PubMedDate not supplied

[Mechanism of ibuprofen and naproxen interaction with endoperoxide prostaglandin synthetase].

The authors studied the pattern and mechanism of ibuprophen and naproxen interaction with endoperoxideprostaglandin synthetase (PGH synthetase) of sheep vesicular glands. The enzymatic activity of PGH synthetase was determined polarographically with the aid of a Clark electrode. Ibuprophen and naproxen were found to inhibit completely PGH synthetase at concentrations of the order of 1 X 10(-5) M. As regards the mechanism of action both the drugs are competitive inhibitors of this enzyme with reference to arachidonic acid and incompetitive inhibitors with reference to adrenaline, an electron donor.

Animals↗

PubMedDate not supplied

[Nature of the interaction of voltaren and other pyrazolone and aniline derivatives with prostaglandin endoperoxide synthetase].

A study was made of the nature and mechanism of interaction of voltaren, butadion, analgin, phenacetin and paracetamol with endoperoxide prostaglandin synthetase (PGH-synthetase) of sheep vesicular glands. Activity of the enzyme was measured by polarography with the aid of a Clark's electrode. Butadion and analgin reversibly inhibited PGH-synthetase at concentrations of the order of 10(-4) M, whereas voltaren at those of the order of 10(-6) M. As regards the mechanism of action, butadion and analgin are competitive inhibitors of PGH-synthetase in respect to arachidonic acid and uncompetitive inhibitors in respect to the electron donor adrenaline. Phenacetin administered at concentrations up to 4 X 10(-2) M did not inhibit PGH-synthetase, whereas paracetamol (10(-3)-10(-2) M) increased its catalytic activity, apparently due to the electron donor properties.

Acetaminophen↗

PubMedDate not supplied

[Kinetics and mechanism of inactivation of isolated chloroplasts].

A detailed kinetic analysis has been performed of a multistep inactivation of chloroplasts. The kinetic model suggested involves the formation of chloroplast forms differing in stability and activity. A comparison of the kinetic model with the experimental data shows that the mechanism of inactivation of isolated pea chloroplasts consists of at least two forms displaying different activity in the Hill reaction and different stability in solution. The effect was studied of the nature of the buffer and destruction products on the kinetics of chloroplast inactivation in the process of "ageing". In phosphate buffer, where the concentration of phosphate exceeds 40 mM, the effect of the destruction products of chloroplasts on their inactivation is insignificant. The pH dependence on the inactivation kinetics suggests that the pH region from 6 to 9 affects only the rapid kinetic process resulting in the increase in the chloroplast activity; irreversible inactivation of chloroplasts is pH-independent. The temperature dependence of the irreversible inactivation kinetics has been studied and the activation parametres of this stage have been determined. Possible molecular mechanism of the limiting stages of the inactivation of isolated chloroplasts are discussed, which can explain the kinetic data obtained.

Chloroplasts↗

PubMedDate not supplied

[Autocatalytic enzyme reactions].

Kinetic aspects of enzymatic reactions proceeding in the autocatalytic mode are considered. Kinetic analysis of a mechanism with proenzyme-enzyme interaction and of mechanism in which activation involves an interaction with the product of enzymatic reaction is presented. It is shown that these mechanisms are distinguished by the dependences of kinetics of the process on enzyme and substrate concentrations. Method is developed for the determination of concentration of active centers of enzyme in the case of activation by reaction product. Conclusions obtained are illustrated using autocatalytic enzymatic systems such as trypsin-trypsinogen and bacterial hydrogenases-hydrogen-4,4'-dimethylbipyridinium.

Bacteria↗

PubMedDate not supplied

[Kinetics of reactions in multienzyme systems. I. Steady state processes in bienzyme systems. Lineal multienzyme sequences].

Kinetic aspects of reactions in multienzyme systems are discussed. Detailed formal-kinetic discription of bienzyme system is made for the steady-state conditions. Two important cases--constant and variable concentration of initial substrate are discussed. The criteria for realization of steady-state condition of system are formulated. Equations which describe the steady rates and steady state concentrations of intermediates as functions of initial concentrations and kinetic parameters of individual enzymes were developed. The time range of steady-state conditions was estimated and methods for the determination of kinetic parameters of enzymes in steady-state condition were developed. The regulation aspects of bienzyme system are considered. An analysis of reactions kinetics in lineal multienzyme systems was made and criteria of steady-state condition were formulated. Methods of determination of kinetic parameters Vmax and Kmax for each individual enzyme of multienzyme system were developed. The principle of limiting step was formulated quantitatively, criteria and methods of the finding of limiting step were developed.

Kinetics↗

PubMedDate not supplied

[Kinetic patterns of bacterial hydrogenase inactivation].

Kinetics of inactivation of hydrogenases is exemplified with the enzyme from Chloropseudomonas ethylica. The effect of gaseous phase, temperature, pH on the inactivation kinetics has been studied. Inactivation of the hydrogenase during incubation of an enzyme solution in air has been studied. Analysis of the kinetic data allowed the conclusion to be made that inactivation involves two forms of the enzyme which differ in their activity and resistance to inactivating actions. Stabilities of the mean time of operation of hydrogenases from Chloropseudomonas ethylica and Thiocapsa roseopersicina are compared. The mechanism of inactivation of hydrogenases from the two sources were found to be similar in many ways.

Air↗

PubMedDate not supplied

[Binding of an acylated plasminogen activator-streptokinase complex with fibrin and the fibrinolytic response in vitro].

Affinity and fibrinolytic properties of streptokinase and two new preparations of acylated plasminogen-streptokinase activator complexes, produced by dissimilar procedures, were studied. Even after 1-min exposure, blood clot lysis carried out by the acyl activating complex was continued in blood plasma more than for 4 hrs, while the streptokinase produced blood clot lysis was accomplished within 1.5 hrs. After 1-min contact with clot in blood plasma the rates of lysis by streptokinase and these acylated plasminogen-streptokinase activator complexes types 1 and 2 constituted 23%, 37% and 63%, respectively, as compared with the rates detected during permanent contact of thrombolytics with blood clot. The activator properties of the thrombolytic agents itself and its stability in blood plasma were of importance even in similar affinity ability of free and acylated activating complexes.

Acylation↗

PubMedDate not supplied

[Single-stranded DNA from plasmid pNB2 in thermophilic bacteria Clostridium thermosaccharolyticum].

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Amino Acid Sequence↗

PubMedDate not supplied

[Kinetic patterns of reactions with immobilized enzymes in open systems].

For studying the properties of immobilized enzyme, a flow reactor is suggested which provides ideal mixing of the reaction components with the granules of immobilized enzyme. To elucidate the mechanism of the reaction and to determine the effective values of maximal rates and Michaelis constants, an analysis of formal kinetic relationships describing the behaviour of the reactor in the stationary and non-stationary regimes has been carried out. The non-stationary kinetics is analyzed both for the case of step-wise and continuous supply of the substrate. A number of equations has been evolved which describe the time dependences of the concentrations of the substrate and reaction products; relationships have been found allowing determination of maximal rates and Michaelis constants from experimental data.

Catalysis↗