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Biomedical subjects

A I Severin

Publications and source records attributed to A I Severin.

At least 19 recordsLinked to original sources
PubMed1991

Isolation, structural and functional characterization of Staphylococcus aureus protoplasts obtained using lysoamidase.

The action of the lysoamidase bacteriolytic complex on Staphylococcus aureus VKM B-209P cells has been studied to obtain protoplasts. The cells in the midlogarithmic phase were the most sensitive to lysoamidase action. It led to local destruction of cell wall due to hydrolysis of the peptidoglycan. Protoplast formation occurred in two steps in the presence of 1 M sucrose. First, osmotically fragile spheroplasts were formed. Then, the protoplasts were released from the destructed cell wall. The protoplast yield was about 80%. The protoplasts preserved the intact ultrastructure and were able to synthesize peptidoglycan fibrillae. Mainly the spheroplasts that maintained the cell-wall residues reversed into bacterial forms. The protoplasts had respiratory activity similar to cells. Respiration of cells and protoplasts was stimulated by various substrates. High rates of oxygen consumption were observed with alpha-glycerophosphate and ethanol as substrates.

Cell Wall↗
PubMed1990

[Hydrolysis of a Staphylococcus aureus cell wall peptidoglycan by 209 P lysoamidase].

Hydrolysis of Staphylococcus aureus 209 P cell wall peptidoglycan was accompanied by the liberation of 1.3 mol of C-terminal and 1.2 mol of N-terminal glycine per mole of Glu as well as of 0.5 mol of N-terminal and 0.3 mol of C-terminal alanine. Gel chromatography on Sephadex G-25, ion-exchange chromatography on QAE-Sephadex A-50 and paper electrophoresis of S. aureus peptidoglycan hydrolysates gave seven homogeneous fractions; these fractions were structurally defined. Lysoamidase hydrolyzed bonds Mur-Ala, Gly-Gly and Mur-GlcN in the peptidoglycan molecule. Hydrolysis of glycan chains was accompanied by the formation of large fragments, (GlcN-Mur)9 and (GlcN-Mur)28. The lytic effect of lysoamidase on S. aureus peptidoglycan is coupled with bacteriolytic enzymes of lysoamidase: acetmuramyl amidase, glycyl--glycine endopeptidase and acetyl--muramidase.

Amino Acid Sequence↗
PubMed1990

[Various physico-chemical and kinetic properties of metalloproteinase from bacteriolytic lysoamidase preparation].

The amino acid composition of metalloproteinase was determined. It was shown that the enzyme is made up of four cysteinyl residues which makes it distinct from other known neutral metalloproteinases from Bacillus brevis, Bacillus subtilis and thermolysine that are devoid of cysteinyl residues. The inhibiting effect of amino acids and some di- and tripeptides on the metalloproteinase activity was studied. The pH-dependence of the Michaelis constant (pKm0) of native and diethylpyrocarbonate-modified metalloproteinase (pKm) suggests that the enzyme active center contains two imidazole groups of histidine with pK alpha 1 = 6.75 +/- 0.1 and pK alpha 2 = 5.4 +/- 0.1. The experimental results are compared to those obtained with other microbial metalloproteinases.

Amino Acids↗
PubMed1989

Chemical composition of Eubacterium alactolyticum cell wall peptidoglycan.

The mechanism of lysis of Eubacterium alactolyticum cell walls by Streptomyces albus G enzyme was studied. The analysis of the peptide terminal groups and peptide subunits isolated from the cell wall digest, released during solubilization of the cell walls, revealed that lytic action of S. albus G enzyme was mainly due to D-alanyl-A2pm endopeptidase, N-acetylmuramyl-L-alanine amidase, N-acetylmuramidase and N-acetylglucosaminidase. E. alactolyticum cell wall peptidoglycan is composed mainly of glucosamine, muramic acid, D-glutamic acid, L- and D-alanine, meso-diaminopimelic acid and glycine. The peptide subunit consists of L-alanyl-D-glutamyl-meso-A2pm-D-alanine. D-Alanine is connected directly with the amino group of the meso-A2pm residue of another peptide subunit. All of the L-amino groups of meso-diaminopimelic acid are involved in cross-linking. The possible structure of the peptide moiety of E. alactolyticum cell wall peptidoglycan is presented.

Amino Acids↗
PubMed1989

Chemical composition of Eubacterium nodatum cell wall peptidoglycan.

The structure of Eubacterium nodatum cell wall peptidoglycan was investigated. The peptide subunit of E. nodatum peptidoglycan has the following structure: L-Ala-D-Glu (Gly)-L-Orn-D-Ala. The carboxyl group of alanine occupying position 4 is attached to the delta-amino group of ornithine of an other subunit by the cross-linking bridge L-Ala-L-Ala-L-Orn. All glycine molecules are connected with the alpha-carboxyl group of glutamic acid with the ratio being 0.5-1. The hydrolysis of E. nodatum peptidoglycan by the S. albus G enzyme proceeds primarily due to the activity of alanyl-alanine endopeptidase, ornithyl-ornithine endopeptidase, ornithyl-alanine endopeptidase, N-acetyl-muramyl-alanine amidase, N-acetylmuramidase and N-acetylglucosaminidase.

Amino Acids↗
PubMed1989

[Study of the inhibition of neutral phosphatase from Pseudomonadaceae by derivatives of its substrates].

The inhibition of neutral phosphatase isolated from the bacteria of the Pseudomonadaceae family by various fragments of the enzyme-hydrolyzed R-O-PO3H2 substrates, inorganic orthophosphate (KH2PO4) and its analogs as well as by adenine, adenosine, alcohols, sugars and amino acids, was studied. It was demonstrated that among other compounds tested only the orthophosphoric acid anions (H2PO4-) exhibit the properties of strong associative inhibitors (K1Vi = 4.35.10(-6)M of the enzyme. The pH dependence of the Michaelis constant [pKm0 = f(pH)] and the inhibition constant for phosphatase by potassium orthophosphate [pK1Vi(KH2PO4) = f(pH)] was studied. The presence in the enzyme active center of a carboxylic (pK = 4.3 +/- 0.1) (presumably, glutamine) and an imidazole (pK = 7.15 +/- 0.1) amino acid residues was postulated. The data obtained were compared to those for neutral, alkaline and acid phosphatases.

Alcohols↗
PubMed1989

[The components of the microbial preparation of lysoamidase from the Pseudomonodaceae family responsible for its bacteriolytic activity].

The contribution of enzymes isolated from the microbial enzymic preparation to its total bacteriolytic activity was studied. The combined action of the lytic proteinase L2 and the lytic fraction L1 used in the same ratio as in the lysoamidase preparation resulted in a complete recovery of the bacteriolytic activity. During a 4-fold increase of the proportion of the lytic enzyme L1 as compared with lytic proteinase L2, the activity of the reconstituted preparation increased by 64%. Neutral phosphomonohydrolase, metal proteinase and the polysaccharide isolated from the lysoamidase preparation had no effect on the bacteriolytic activity of the reconstituted preparation. The polysaccharide isolated from lysoamidase increased the thermal stability of the preparation obtained up to that of lysoamidase.

Bacteriolysis↗
PubMed1988

[Lytic ability, in relation to gram-positive microorganisms, of a preparation isolated from a Pseudomonas lytica culture].

A lytic enzyme isolated from P. lytica was studied with respect to its effect on pathogenic grampositive and gramnegative organisms. All the grampositive organisms were lyzed by the enzyme to this or that extent. The cells of staphylococci were the most sensitive. The gramnegative organisms were resistant. It was suggested that the lytic enzyme could be used in preparing drugs for treating certain skin diseases caused by pathogenic staphylococci.

Bacteriolysis↗
PubMed1986

[Various physico-chemical properties of lytic proteinase L2 of the enzyme preparation lysoamidase isolated from bacteria of Pseudomonadaceae family].

Some physico-chemical properties of lytic proteinase L2 isolated from the enzymatic microbial preparation of lysoamidase were studied. The molecular mass of the enzyme is 15 000 Da, pI is 5.3. The enzyme hydrolyzes casein as well as the cells and cell walls of Staphylococcus aureus 209-P. The pH optimum of casein hydrolysis lies at 9.5; that for cell wall hydrolysis at 8.0. The temperature optimum for casein hydrolysis and cell lysis lies at 55 degrees C and 65 degrees C, respectively. The enzyme proteolytic activity is inhibited by serine proteinase inhibitors in a greater degree than the lytic activity. 50% of the proteolytic and lytic activities is lost upon enzyme heating for 15 min at 65 degrees C.

Bacteriolysis↗
PubMed1981

Protein composition of Bdellovibrio bacteriovorus and Escherichia coli membranes during their interaction.

A comparative study of membrane proteins of Bdellovibrio bacteriovorus and host-bacteria Escherichia coli was performed by polyacrylamide gel electrophoresis in presence of sodium dodecyl sulphate. Infection of E. coli cells by bdellovibrions resulted in the loss of some high-molecular proteins and appearance of new ones in the host-bacteria membranes. The possible role of parasite proteases in degradation of host-bacteria membrane proteins is discussed.

Bacterial Proteins↗
PubMed1978

Metabolic and genetic control of isoenzyme spectrum of alkaline phosphatase in Escherichia coli.

Three proteins possessing alkaline phosphatase activity were detected in a fraction of periplasmic material of Escherichia coli K-10 and its mutants with constitutive synthesis of alkaline phosphatase. They also showed acid phosphatase, pyrophosphatase and ATPase activities. Through the use of phosphatase-negative mutants it was shown that these proteins were the products of a single structural gene and therefore represented alkaline phosphatase isozymes. The numbers of enzyme isoforms and possibly the spectrum of their phosphohydrolase activities were controlled by exogenous orthophosphate and depended on the integrity of regulator genes for alkaline phosphatase.

Acid Phosphatase↗
PubMed1976

[Escherichia coli membrane-bound polyphosphatase].

A complex of polyphosphatase with E. coli membranes has been isolated and studied. It is shown by gel-filtration through G-200 Sephadex and centrifugation in sucrose concentration gradient that about 5% of polyphosphatase total content in cells is bound with the heterogenous fraction containing smooth membranes and the ribosome-membrane complex. On the basis of the data obtained it is suggested that the formation of a complex of polyphosphatase with membranes is a stage of synthesis and secretion of this enzyme to protoplasm.

Escherichia coli↗
PubMed1976

[Effect of detergents and proteolytic enzymes on membrane-bound phosphohydrolases in Escherichia coli cells with repressed and depressed biosynthesis of these enzymes].

Solubilization of protein membranes by detergents and protein liberation from the membranes induced by proteolytic enzymes results in a change of activity of membrane-bound phosphohydrolases--alkaline phosphatase and polyphosphatase. The activity of enzymes under conditions of repressed and derepressed biosynthesis of phosphohydrolases changes differently, thus indicating their different membrane environment in the two types of membranes. Some data were obtained on the localization of alkaline phosphatase in a hydrophobic region, possibly in lipid bilayer and polyphosphatase in the surface layers of the membrane.

Binding Sites↗
PubMedDate not supplied

[Enzymes of a bacteriolytic lysoamidase preparation. Various properties of bacteriolytic protease L2].

Bacteriolytic proteinase L2 is able to cleave fluorogenic synthetic tripeptide anthranoyl-alanyl-alanyl-phenylalanyl-nitroanilide (Abz-Ala-Ala-Phe-pNA) at the bond between phenylalanine and p-nitroaniline. Optimal conditions of the tripeptide cleavage have been determined: pH 6.7 + 0.1; mu = 2 (by NaCl); t = 40 degrees C; KM = 2.6 x 10(-5) M. Metal cations reduced the enzyme activity. The enzyme was inhibited by EDTA, p-CMB, DIF. The synthetic tripeptide can be used to determine the activity of the L2 enzyme.

Amino Acid Sequence↗