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Biomedical subjects

L V Kozlov

Publications and source records attributed to L V Kozlov.

At least 37 records · Page 2Linked to original sources
PubMed1985

[Effect on human complement of blastolysin and the glycopeptide (MDP and GMDP) and carbohydrate fragments of peptidoglycans].

Along with complement activation by the classical pathway, blastolysin, an antitumor and adjuvant preparation of Lactobacillus bulgaricus peptidoglycans, effectively inhibits the transformation of C3 in to C5 convertase. Values of inhibition maximum and dissociation constants of the reversible C3b-acceptor complex for blastolysin and main immunological active structural moieties of peptidoglycans (GMDP, MDP) and their inactive carbohydrate components (N-acetylglucosaminyl-N-acetylmuramic acid, N-acetylglucosamine, and N-acetylmuramic acid) have been determined. Immunostimulator concentrations for blastolysin, GMDP, and MDP in inhibition of the C5 convertase formation (C3b binding) correlate with their doses in vivo (animal blood), displaying antitumor activity.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1985

[Changes in the ultrastructure of subcomponent C1q of human complement during spontaneous inactivation in diluted solutions].

Dilution of human serum or solutions of highly purified subcomponent C1q of human complement results in the drop of C1q activity. Electron microscopy of highly purified subcomponent C1q revealed that a certain part of molecules has a changed ultrastructure and C1q subunits are dissociated. As the preparations for electron microscopy have been obtained from dilute solutions, the changes in the ultrastructure and C1q inactivation should be interrelated phenomena. The conformational liability of the C1q structure is supposed to have a functional role.

Complement Activating Enzymes↗
PubMed1985

[Complement fixation activity of immunoglobulin G in ethylene glycol solutions].

Affinity of IgG to the first complement factor C1q was found out to increase in 10-30% glycol solutions. Analytical ultracentrifugation and turbidity data showed that IgG molecules do not aggregate at such concentrations of glycol. The complement-binding effect may be caused by a conformational transition in the IgG molecules.

Animals↗
PubMed1984

[Binding and activation of the first component of human complement on artificial matrices].

Artificial sorbents that comprise macroporous glass covered by the copolymer of N-vinylpyrrolidone and N-substituted acrylamide have been synthesized. Aminoethanol is bound to acrylic acid residue in one sorbent (AE-glass), whereas the other sorbent involves immunoglobulin G with the hexamethylenediamine spacer (IgG-glass). C1q binds specifically to IgG-glass with Ka 4,07(+/- 0,32) X 10(7) M-1. Free energy of the C1q binding to IgG-glass is twice higher than that of its binding to monomeric IgG. This evidences that one C1q molecule associates with two IgG molecules of the sorbent. A weak nonspecific sorption of C1q to AE-glass was found. Both specific (on IgG-glass) and nonspecific (on AE-glass) sorption of the first component of complement activate the classical pathway in human serum as manifested in the consumption of the C4, C2, C3 and C5 components. IgG-glass was employed for C1q isolation from human serum by affinity chromatography, whereas unbound part of serum may be used as a reagent R1q. The yield of highly purified C1q after IgG-glass affinity chromatography and gel filtration on Sephacryl S-300 is 63,6%.

Chemical Phenomena↗
PubMed1984

[A new low molecular-weight protein effector of human complement from the venom of the Central Asian cobra Naja naja oxiana].

Six protein effectors of human complement were isolated from the whole venom of the Central Asian cobra Naja naja oxiana. Three of them have acidic properties and molecular weights of 61 000, 5000 and 3000, and the rest are basic proteins with molecular weights of 54 000, 9000 and 7000. Two low molecular weight basic proteins CFB-II and CFB-III are isolated in as high amounts as 115 and 85 mg per g of dry venom. All the effectors inhibit the classical pathway of complement activation and, with the exception of CFB-II and CFB-III, the alternative pathway. The latter, on the contrary, enhances the alternative pathway of activation. N-Terminal sequence determination for CFB-III demonstrated its identity to the earlier characterized cytotoxin II. The action of CFB-III on the classical pathway of complement activation consists in the component C4 inactivation. A mechanism for the CFB-III activation of the alternative pathway is proposed implying the CFB-III induced transformation of the C3 component into a C3b-like one producing a soluble C3 convertase.

Chromatography, Gel↗
PubMed1983

[Effective method of simultaneous isolation from human serum of highly purified factors B and D of the alternative pathway of complement activation].

A simple method for isolation from human serum of the complement alternative pathway factor B, in a yield over 40% and purity over 80% with respect to protein, has been developed. Such a high yield was reached due to rejection of ammonium sulphate fractionation and employment of only two chromatographic stages: on CM-Sephadex C-50 and on DEAE-Sepharose CL-6B. An additional chromatography on QAE-Sephadex A-50 provides factor B of 100% purity but with a loss of some amount of protein (yield approximately 20%). One of the fractions, obtained at the first stage of factor B purification, contained also factor D. After rechromatography on CM-Sephadex C-50 and gel filtration on Sephadex G-75 it afforded factor D in yield more than 60% and purity above 100%.

Chromatography, DEAE-Cellulose↗
PubMed1983

[A mechanism of human complement activation by immunostimulators from the bacterial cell wall].

Effects on the human complement system of the cell wall preparations: lipopolysaccharides and polysaccharides of E. coli, Salmonella typhi (pyrogenal, salmosan), Bact. prodigiosum (prodigiosan) and peptidoglycan of Lactobacillus bulgaricus (blastolysin) have been studied. Lipopolysaccharide of E. coli, pyrogenal and salmosan were found to bind efficiently the first complement factor C1q. The constants for inhibition of the C1q binding to antibodies by the mentioned preparations were determined, and their ability to initiate the classical pathway of complement activation (consumption of C4, C2 and C3 factors) was assayed. These preparations only slightly affect the alternative pathway. Prodigiosan, not influencing the classical pathway, initiates the alternative one. Its binding constant with the activated Bb factor was determined. This constant reflects the Bb association with C3b and is (2,4 +/- 0,1) x 10(7) mole-1 l. Blastolysin is effective both in the C1q binding and initiation of the alternative pathway of complement activation. Immunostimulating activity of the bacterial cell wall preparations seems to involve activation of the complement system and the release of the fragments from the complement factors which are mediators of the immune response.

Anti-Bacterial Agents↗
PubMed1982

[Thermodynamics changes in catalytic properties of immobilized enzymes].

Study of the temperature dependence of hydrolysis of the ethyl ester N-acetyl-L-tyrosine and p-nitroanilide N-succinyl-L-phenylalanine by chymotrypsin and polymaleic acid-modified chymotrypsin showed that the enthalpy and enthropy of dissociation of the enzyme-substrate complex and those of activation of the enzyme acylation in the course of catalysis increase during the native enzyme transition to its modified form. The data obtained can be explained terms of changes in the native conformation of the enzyme during its modification, which is confirmed by the previously obtained data on thermodenaturation. Some part of the energy of substrate binding is consumed for changing the conformation of the modified protein, rendering it close to the native one and thus providing a further enzymatic catalysis which is similar to that by the native enzyme.

Chymotrypsin↗
PubMed1981

[Free energy linearity principle in enzymatic catalysis and thermodynamic principles of specificity].

It was demonstrated that the free energy linearity principle, i.e. relationship between the kinetics and thermodynamics of enzymatic reactions, can be applied to enzymatic hydrolysis of specific substrates of chymotrypsin, thus suggesting that the substrate binding energy can be utilized for decreasing the activation barrier of the reaction. The literary data support the applicability of the free energy linearity principle to enzymatic reactions catalyzed by some hydrolytic enzymes.

Catalysis↗
PubMed1981

[Mechanism of thermal denaturation of native trypsin and trypsin modified by neutral soluble polymer].

The thermal denaturation of trypsin solutions and trypsin vinylpyrrolidone-acrolein copolymer conjugate was studied within the temperature range of 37.5-96 degree. pH 4.5. A mechanism for trypsin thermal denaturation based on its ability to form dimers and determining the minimal stability of the enzyme at 66 degree and its maximal stability at 74 degree is proposed. The thermal denaturation of the trypsin conjugate is of a different type, which depends on the changes in the thermal denaturation mechanism due to its incapability to form dimers. A decrease in the activation and thermodynamic parameters of the enzyme denaturation during its modification is due to the approximation of the protein structure to that of the denatured form, eventually resulting in the enzyme destabilization. The increased stability of the modified protein to the denaturating effects of low temperatures is due to the changes in the denaturation mechanism induced by enzyme modification.

Acrolein↗
PubMed1980

[Enzyme intermediates with the C-terminal products of substrate hydrolysis by carboxypeptidase A and chymotrypsin. Use of the free energy linearity principle].

Based on the correlation between the kinetics and free energy of enzymatic reactions of hydrolysis (i. e. free energy linearity principle) for peptide and ester substrate hydrolysis by carboxypeptidase A, the identity of the catalytic mechanism for these substrates and the lack of formation of an activated enzyme intermediate with the C-terminal part of the hydrolyzed substrate were demonstrated. Using the energy linearity principle to the hydrolysis of specific peptide substrates by chymotrypsin, the nature of the activated enzyme intermediate with the C-terminal part of the substrate as a complex with a non-ionized product can be postulated. This accounts for the transpeptidation (according to the amino transfer type) of the peptides with an unprotected carboxylic group. It was concluded that the formation of the enzyme intermediate with the C-terminal part of the hydrolyzed substrate for all the three main classes of proteinases, i. e. serine, carboxylic and metal enzymes, occurs via different mechanisms.

Carboxypeptidases↗
PubMed1979

[Principle of free energies linearity in chymotrypsin catalysis].

The applicability of the previously described principle of free energies linearity for semispecific substrates of chymotrypsin for the derivatives of acetylphenylalanine, acetyltryptophane and acetyltyrosine was demonstrated. The pH dependence of the parameters of a linear equation describing the relationship between the free energy of hydrolysis and the logarithmus of the kcat/Km(app) ratio suggests that at optimal pH the stability of the activation barrier of enzyme acetylation for all semispecific substrates is observed.

Chymotrypsin↗
PubMed1979

[Dependence of pepsin conformational states on pH and temperature].

A conformational behaviour of pepsin depending on pH and temperature was studied by circular dichroism, differential UV-spectroscopy, calorimetry and enzymatic hydrolysis kinetics. A subtile conformational transition of the enzyme accompanied by changes in the physico-chemical and enzymatic properties of the protein was observed within the temperature interval of 15--40 degrees and within the pH range of 1,1--5,6. The range of pepsin heat denaturation was studied. A diagram of pepsin conformational states under different values of pH and temperature was built.

Calorimetry↗
PubMed1979

[Nature of the intermediate compound formed during catalysis by pepsin].

The applicability of the free energies linearity principle to catalysis by pepsin may indicate that the mechanism of formation of a covalent pepsin intermediate with the second (amine or alcohol) part of the hydrolyzed substrate is a true one. The choice has been made from consideration of three possible types of mechanisms covalent binding, complex with a nonionized NH2-group and the absence of an activated intermediate.

Enzyme Activation↗
PubMed1979

[Steady-state kinetics of reactions catalyzed by serine sulfhydrases of Saccharomyces serevisiae].

The steady-state kinetics of the two substrate reaction of L-cysteine desulfation in the presence of 2-mercaptoethanol catalyzed by serine sulfhydrase from bakers yeast -- a pyridoxal phosphate-containing enzyme of the beta -- substituting lyase type -- were studied. Highly purified enzyme preparations (approximately 90% purity) of Saccharomyces cerevisiae with specific activity of 25 mumoles of H2S per 1 hr per mg of protein were used. The values of V, KS1, KS2 and alpha were calculated from the initial rates of the reaction under constant concentration of L-cysteine (S1) and variable concentration of 2-mercaptoethanol (S2) and vice versa. The data obtained suggest that under conditions of a two-substrate reaction catalyzed by serine sulfhydrase and in case of beta-cyanoalanine synthase of blue lupin the substrate binding to the enzyme is interdependent and obeys a unordered mechanism with o formation of a ternary aminosubstrate-pyridoxal phosphateenzyme-cosubstrate complex (alpha = 2.6).

Cystathionine beta-Synthase↗