Biomedical subjects

O A Kost

Publications and source records attributed to O A Kost.

33 records · Page 2Linked to original sources

PubMed1994

[Determination of solvent accessibility of residues of aromatic amino acids in proteins using the second derivative of the UV-absorption spectrum].

A new method for determining the solvent accessibility of tyrosine and tryptophan residues in proteins from the wavelengths of absorption peak maxima in secondary derivatives of UV absorption spectra has been developed. Analytical expressions for calculating the number of groups in latent and exposed states of amino acid residues in protein globules were obtained on the basis of the previously elaborated mathematical model of spectral changes observed during the transition between those respective states. The new procedure was used to analyze sixteen proteins and showed a good correlation between the experimental results and literary data.

Models, Theoretical↗

PubMed1994

[A quantitative method for evaluating the structure and conformational stability of proteins by second derivative UV-spectroscopy].

A quantitative method is suggested for estimating the structure and conformational stability of proteins based on the individual absorbance of Tyr residues in the second derivative UV spectra. Subtilisins Carlsberg, BPN' and 72 were chosen as the model proteins. The values of the increase of the Tyr absorption at 282.3 nm upon the total denaturation of the proteins made it possible to calculate the number of the exposed and "buried" tyrosine residues in the native proteins. A mathematical model of spectrum changes during the transition of Tyr residues from the "buried" to exposed form is suggested. The method is useful for the determination of the denaturation constants of proteins bearing "buried" tyrosine residues.

Models, Theoretical↗

PubMed1990

[Zinc-dependent angiotensin-converting enzyme in reactions with various enzymes].

The effects of Zn2+ on the activity of the angiotensin-converting enzyme from bovine lung towards the substrates, FA-Phe-Gly-Gly and Cbz-Phe-His-Leu, have been studied. At pH below 7.0 zinc ions added to the reaction mixture increase the enzyme activity; this stimulating effect is changed to inhibition with a further rise in Zn2+ concentration. It was shown that the dissociation constant for the enzyme--Zn2+ complex and the "optimal" concentrations of Zn2+ needed for the manifestation of the maximal enzymatic activity depend on the nature of the substrate at all pH values studied.

Amino Acid Sequence↗

PubMed1990

[Function of angiotensin-converting enzyme on matrices].

The binding of the angiotensin-converting enzyme from bovine lung on BrCN-activated Sepharose, CH- and AH-Sepharoses as well as on AH-Sepharose via the carbohydrate fragment of the glycoprotein molecule modulates the possible microenvironment of the enzyme in vivo. It has been shown that the close interaction of the enzyme with the carbohydrate matrix may increase the absolute values of catalytic constants for the hydrolysis of certain substrates. The binding of the angiotensin-converting enzyme to the matrices markedly changes the enzyme activation by chloride ions by causing a shift in the activity optima towards lower activator concentrations.

Amino Acid Sequence↗

PubMed1990

[Physico-chemical characteristics of angiotensin-converting enzyme from the bovine lung].

The angiotensin-converting enzyme from bovine lung was isolated by chromatography with a 25-30% yield and purified 2200-2600-fold. The active molecule concentration in the enzyme preparations was 70-100% as could be judged from titration by inhibitor SQ 20,881. The molecular mass of the enzyme according to electrophoretic data is about 132 kDa; the maximal radius of the enzyme molecule as determined by electron microscopy is 68 +/- 9 A. Five enzyme isoforms with pI of 4.85, 4.7, 4.54, 4.38 and 4.3, respectively, were identified. The kinetic parameters of hydrolysis of three synthetic peptide substrates and the constants of activation of the substrate (Z-Phe-His-Leu) hydrolysis by chloride anions were determined.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1982

[Structure of the active center of subtilisin 72].

The inhibition by N-benzoyl-L-arginine of subtilisin-catalyzed hydrolysis of various substrates was investigated. Study of combined hydrolysis of these substrates revealed the existence of two productive binding sites in the subtilisin 72 molecule. The type of substrate adsorption depends on the nature of the acyl moiety of the molecule and on the nature of the split-off group. The N-acetyl-L-tyrosine ethyl ester and N-benzoyl-L-citrulline methyl ester are bound at the same adsorption site (A), while N-cinnamoyl imidazole and N-acetyl-L-valine methyl ester are found at another adsorption site (B); N-benzoyl-L-alanine methyl ester can be adsorbed both at site A and at site B. However, substitution of the split-off group in the substrates previously adsorbed at site B by the p-nitrophenyl group causes their transfer to site A.

Arginine↗

PubMedDate not supplied

New feature of angiotensin-converting enzyme: carbohydrate-recognizing domain.

Self carbohydrate-mediated dimerization of glycoprotein angiotensin-converting enzyme (ACE) was demonstrated. The dimerization was studied in the reverse micelle experimental system as a model of biomembrane situation. Asialo-ACE or agalacto-ACE was able to form a dimer, whereas deglycosylated ACE and sequentially desialylated and degalactosylated ACE failed to dimerize. ACE-ACE interaction was competitively inhibited by Neu5Ac- or Gal-terminated saccharides. The results have allowed us to propose the existence of carbohydrate-recognizing domain (CRD) on ACE molecule. The structural requirements of this CRD were estimated based on the ability of saccharides to inhibit ACE dimerization. The most effective monosaccharides with equal inhibition potencies were shown to be galactose (as GalbetaOMe) and N-acetylneuraminic acid (as Neu5AcalphaOMe). Among oligosaccharides, the most effective ones were found to be 3'SiaLac and, especially, the whole pool of ACE oligosaccharide chains and biantennae complex oligosaccharide chains of other glycoproteins. Bovine and human ACEs were shown to be similar in terms of recognition of carbohydrates.

Animals↗

PubMedDate not supplied

[Structure-functional features of homologous domains of angiotensin-converting enzyme].

Somatic angiotensin-converting enzyme (ACE) consists of two homologous domains, each of them containing an active site. Differences in substrate specificities and affinity to inhibitors of the active sites of the two domains of bovine ACE are described. The ACE domains demonstrate different thermostability, and the reasons for this difference are analyzed. A structural model of the ACE domains is suggested, which allows us to reveal the structural subdomain important for the protein stability and localize the hydrophobic and the carbohydrate-binding sites.

Amino Acid Sequence↗

PubMedDate not supplied

[Radiation activation of angiotensin-converting enzyme during low-dose irradiation].

Radiation activation of angiotensin-converting enzyme (respect to Cbz-Phe-His-Leu as substrate) was obtained at the gamma (137Cs, t(irr) = 10s-2h, D approximately 3 Gy)- and X (plasma foces source, t(irr) = 10(-9)s, Cu-filter, D approximately 2 x 10(-5) Gy)-irradiation. The inactivation of the horseradish peroxidase at the same X-irradiation dose (2 x 10(-5) Gy) took place. Based on the experimental data and on the mathematical model proposed by us we made a conclusion that the special points exist on the dose response curves. Besides, the deduction that an activation is a common process at radiation changes of the different enzymes follows from our model. The activation of tobacco peroxidase (in presence of Ca(2+)-cations and without them) and of recombinant horseradish peroxidase (in presence of H2O2) by gamma-irradiation was really observed (respect to guaiacol as substrate).

Animals↗

PubMedDate not supplied

[The role of angiotensin-converting enzyme in pathogenesis of post-contusion disorders of ophthalmotonus and hemodynamics].

Angiotensin converting enzyme (ACE) activity was studied in tear fluid of the contusion injured eye. We found substantial decrease of ACE activity during 1 month after trauma. Reduced ACE activity can potentiate kinin action and may contribute to the maintenance of reduced vascular tone, high capillary permeability inducing ciliochoroidal effusion which leads to ocular hypotony. We have found decrease of ACE activity in another healthy eye.

Eye Injuries↗

PubMedDate not supplied

[Experimental validation of licopin-containing drug tomatol use in combined therapy of patients with diabetic retinopathy].

Effects of tomatol on metabolic changes in the blood and lacrimal fluid and ocular capillaries of rabbits with alloxane diabetes were studied. Tomatol is a drug containing licopin carotenoid characterized by a high biological activity. The intensity of lipid peroxidation was notably decreased, antioxidant activity of the blood increased, lipid metabolism parameters in the blood and some parameters of proteinase inhibitory balance in the blood and lacrimal fluid normalized in diabetic rabbits treated with tomatol in comparison with untreated rabbits. Changes in perilimbic capillaries were less expressed in treated vs. untreated animals. Hence, tomatol is recommended for combined therapy of patients with diabetes as a drug normalizing metabolism and probably decelerating the development of diabetic retinopathy.

Alloxan↗

PubMedDate not supplied

[Radioenzymatic investigation of membrane and soluble forms of angiotensin-converting enzyme in acetate-phosphate buffer].

The dose response of soluble and membrane forms of angiotensin-converting enzyme to gamma-irradiation is investigated at different pH values of the medium and at different concentrations of acetate-phosphate buffer. Membrane form of the enzyme is more stable shows principally other conformational equilibrium than the soluble form. "Splitted" activation peaks on the curves of the enzyme dose response are observed.

Acetates↗

PubMedDate not supplied

[Activity of angiotensin-converting enzyme in the blood and tear of patients with diabetic retinopathy].

There have recently been data on the important role of the renin-angiotensin system (RAS) in the pathogenesis of diabetes mellitus and its complications; however, the relationship of systemic and local RAS to the development of diabetic retinopathy (DR) remains little studied. This study determined the activity of angiotensin-converting enzyme (ACE), the key enzyme of RAS in the blood and tear of patients with DR. There was an increase in the blood activity of ACE and a decrease in its lacrimal activity as compared with their normal levels. A relationship was found between the activity of ACE in the blood and tear, on one hand, and the stage of DR, the type of diabetes mellitus, its severity and compensation, and the presence of nephropathy in a patient, on the other.

Adolescent↗

PubMedDate not supplied

[Azoalbumin hydrolysis by Bacillus subtilis 72 subtilisin].

The kinetic parameters of azoalbumin hydrolysis by alkaline proteinase from Bacillus subtilis were determined to be Km = 1.2 . 10(-3) M, kcat = 1.5 sec-1 according to the method of Lainuiwer-Berk and Km = 4 . 10(-3) M, kcat = 0.5 sec-1 from the analysis of the entire kinetic curve. It was found that pH optimum of subtilizin hydrolysis of various substrates and the shape of the curve depended on the substrate nature.

Albumins↗

PubMedDate not supplied

[Activity of angiotensin-converting enzyme in the rabbit lacrimal fluid after burn of the cornea].

In the experimental model of severe alkaline burns of the rabbit cornea we found the dependence of angiotensin-converting enzyme activity in tears upon both the time periods and the degree of inflammation. It was indicated that the enzyme activity in tears of animals with ulceration of deep tissues of cornea was much higher than in tears of animals with surface erosion of cornea.

Animals↗