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Biomedical subjects

M M Rakhimov

Publications and source records attributed to M M Rakhimov.

At least 19 recordsLinked to original sources
PubMed1989

[Purification of phospholipase C isoenzyme 1 from Clostridium perfringens and its properties].

A procedure for the purification of isoenzyme I of phospholipase C from Cl. perfringens was developed. The isoenzyme was purified to homogeneity (data from disc electrophoresis) using affinity chromatography on polycephamide and gel filtration through Ultrogel AcA-54, the enzyme yield being 41%. Some properties of the purified isoenzyme I (pH and temperature optima, stability, effect of metal ions and detergents, substrate dependence) were investigated. No significant differences between the properties of the unfractionated enzyme and isoenzyme I were established.

Cations, Divalent↗
PubMed1989

[Changes in the phospholipid composition of mitochondria during heat incubation].

Incubation of liver mitochondria at 37 degrees C causes changes in the phospholipid composition, such as the decrease in the levels of major phospholipids (e.g. phosphatidylcholine, phosphatidylethanolamine, cardiolipin) and their lysoderivatives as well as an increase in the levels of phosphatidic and lysophosphatidic acids. Similar changes in the phospholipid composition are observed upon heat incubation of mitochondrial fragments ("ghosts", inner and outer mitochondrial membranes). Ca2+ accelerate the heat-induced changes in the phospholipid levels resulting from heat incubation, whereas EGTA, in contrast, decelerates them. The role of an endogenous system of lipolytic enzymes in the observed conversions of mitochondrial phospholipids is discussed.

Animals↗
PubMed1989

[Properties of phospholipase D from rat liver mitochondria].

The properties of membrane-bound mitochondrial phospholipase D were investigated. The enzyme was shown to catalyze the hydrolysis of endogenous mitochondrial phospholipids, particularly phosphatidylethanolamine. The phospholipase activity was maximal at pH 5.0 and 7.0 was stimulated by Ca2+ and sodium oleate and was inhibited by SDS. The conditions for solubilization of the mitochondrial enzyme and its adsorption on a biospecific adsorbent were elaborated. The adsorption resulted in a 17-fold purification of the enzyme with a 33% yield. The adsorbed enzyme, similar to the membrane-bound one, was activated by Ca2+ and sodium oleate but, in contrast to the latter, was able to catalyze the hydrolysis of an exogenous substrate.

Animals↗
PubMed1988

[Properties of phospholipase A2 from inner and outer mitochondrial membranes].

The catalytic properties of membrane-bound phospholipase A2 from inner and outer mitochondrial membranes were studied. Differences were found in the properties of phospholipase A2 during the hydrolysis of both endogenous and exogenous substrates, i.e. the dependence of the hydrolysis rate on pH, temperature, bivalent metal ion concentrations and EDTA. It was demonstrated that purification and adsorption immobilization of the inner mitochondrial membrane enzyme on biospecific adsorbent cause changes in the enzyme catalytic properties. The role of phospholipase A2 microenvironment in the manifestation of the enzyme activity and catalytic properties is discussed.

Animals↗
PubMed1988

[Purification and properties of lysophospholipase from the venom of the giant hornet Vespa orientalis].

Using biospecific chromatography on polylysocephamide, a toxic phospholipase possessing a presynaptic effect on neuromuscular preparations was isolated from the venom of the giant hornet Vespa orientalis. The enzyme was shown to possess a high hydrolytic activity towards 1-acyllysophosphatidylcholine within a narrow pH range (pH optimum 7.5). The enzyme activity was suppressed by detergents of various chemical composition. Lysophospholipase caused an intensive hemolysis of washed human erythrocytes. The catalytic and hemolytic functions of the enzyme were sensitive to metal ions, however, in a different degree. Ca2+ and Mn2+ activated, while Cu2+ and Zn2+ inhibited the enzyme. Mg2+ and Sr2+ had no effect on the enzyme activity.

Bee Venoms↗
PubMed1984

[Properties of phospholipase A2 from the venom of the large hornet Vespa orientalis].

Some properties (catalytic and hemolytic activity, pH and temperature optima, stability, substrate specificity, effects of detergents and metal ions, N-terminal sequence, chemical modification of histidine in the enzyme active center, etc.) of phospholipase A2 from hornet (Vespa orientalis) venom were studied. It was shown that phospholipase A2 from hornet venom differs essentially from other enzymes of this species in terms of stability, catalytic properties and structural features. The active center of the enzyme contains an essential histidine residue, similar to other phospholipases A2 from various sources. Unlike other known forms of phospholipase A2, the enzyme under study exerts a pronounced hemolytic action. The hemolysis is inhibited by Ca2+ at concentrations capable of inducing the activation of the hydrolytic activity of the enzyme.

Amino Acid Sequence↗
PubMed1983

[Properties of lipases from Oospora lactis].

The procedure of isolation and purification of lipases from the fungus Oospora lactis have been developed. The existence of two different lipases has been demonstrated, one of which (Mr = 43000) is localized in the periplasmic space and can be liberated into the external medium in an unchanged form, while the other (Mr = 40000) is tightly bound to the membranes and can be solubilized by detergent treatment. The most essential properties of the lipases are discussed and a detailed analysis of the functional and physicochemical properties of extracellular lipase is given.

Cell Membrane↗
PubMed1983

[Functional state of the mitochondria of the small intestine mucosa during heat stress].

Rate of respiration and effectiveness of oxidative phosphorylation of intestinal mucosa mitochondria in rats revealed that adaptation to heat loads is accompanied by reversible switching over of the NAD-dependent and succinate ways of mitochondria oxygenation which maintains the normal existence of mucosal cells in conditions of heat stress. Severe heat stress disturbs the functional integrity of the oxygenation switching over and leads to disturbances of the rate of oxygenation and effectiveness of oxidative phosphorylation.

Adaptation, Physiological↗
PubMed1982

[Role of calcium ions in the development of the catalytic activity of phospholipase D].

The peculiarities of the reaction of mycellar lecithine cleavage by phospholipase D and the role of Ca2+ in the catalytic activity of the enzyme were studied. It was shown that Ca2+ participates in the formation of a catalytically active intermediary enzyme-substrate complex with a strict stoichiometric ratio of substrate, phospholipase activator (Na-DS) and Ca2+. The kinetics of inhibition for this reaction by lantane and fluoride ions and EDTA were studied. The inhibition of the reaction in a lecithine-Na-Ca2+-phospholipase D system by La3+ is due to substitution of bivalent Ca2+ by trivalent La3+ within the intermediary complex. The inhibiting effect of F- is due to penetration of the electron-negative ion into the coordination sphere of the intermediary complex and to disturbances in the hydrophobic binding between the ligands. The inhibitory action of EDTA is revealed during protein binding to the substrate and is not due to the chelating capacity of EDTA with respect to Ca2+. It was demonstrated that the role of Ca2+ is not restricted by its binding to phospholipase C. Ca2+ are also necessary for neutralization of the extra charge on the surface of substrate mycelles, production of an appropriate ionic strength and modification of the substrate phase surface at the interface. The catalytic function of Ca2+ consists in a formation of a "recognition" site in the active center of phospholipase D.

Calcium↗
PubMed1982

[Separation and properties of molecular forms of phospholipase D from plants].

The optimal conditions for isolation and purification of phospholipase D (EC 3.1.4.4) from Middle-Asian radish tubers, cotton plant seeds and cabbage leaves using biospecific chromatography on polyamide absorbent with covalently linked phosphatidylethanolamine, were elaborated. The synthetic absorbent can be used for separation of molecular enzyme forms differing in their affinity for immobilized phosphatidylethanolamine (forms I, II, and III). Experimental evidence for the interconvertibility and interrelationship of different forms of plant phospholipase D is given. It is demonstrated that forms I and III separated by biospecific chromatography are represented by enzyme conformers distinguishable by their thermal stabilities (phospholipases D1 and Ds, respectively), while form II is a high molecular weight phospholipase D.

Chromatography, Affinity↗
PubMed1981

[Some properties of cotton plant phytase].

Some properties of phytase from cotton plant seeds were studied. The phytase activity was shown to increase during seed germination. The enzyme from cotton sprouts is not activated by Ca2+, Mg2+ and K+ and has the pH optimum of 5,0 and temperature optimum of 50 degrees. The molecular weight of the enzyme as determined by gel-filtration is 36000.

6-Phytase↗
PubMed1981

[Interaction of cytotoxin and Ca2+ with phospholipase A2].

The effects of Ca2+ and cytotoxin from Middle Asian cobra venom on the hydrolytic activity of phospholipase A2 from the same source and on its action on erythrocyte membrane phospholipids and mitochondria were studied. The necessity of phospholipase A2 for Ca2+ depends on the type of substrates (phosphatidyl methanol, phosphatidyl ethanol, cephalin, phosphatidyl ethyleneglycol, phosphatidyl inositol), whereas enzymatic cleavage of lecithin can also occur in the absence of Ca2+. Cytotoxin Vc" I had no effect on the rate of phospholipid hydrolysis in the absence of Ca2+. However, in the presence of Ca2+ cytotoxin at low concentrations activated phospholipase A2, while its high concentrations inhibited the phospholipid hydrolysis with the exception of phosphatidyl ethyleneglycol and phosphatidyl inositol. In experiments with purified phospholipids no synergistic effect of cytotoxin and phospholipase A2 was observed. The activating effect of cytotoxin and phospholipase A2 was comparable to that of the cationic detergents. The effect of phospholipase A2 on erythrocyte hemolysis and succinate oxidation by mitochondria was more complicated: the activating or inhibiting effect depended on the state and ratio of Ca2+, cytotoxin and phospholipase A2. It is suggested that the synergistic effect observed in membrane systems is primarily due to the structural organization of the membranes and the phase condition of the membrane phospholipids.

Animals↗
PubMed1981

[Properties of phospholipase D from Raphanus sativus].

The main properties of phospholipase D from radish roots were studied. The effects of various activators including Ca2+ on the catalytic activity of the enzyme were determined. The necessity for Ca2+ is in a large degree dependent on the type of the prime, as well as on the substrate type. Sodium dodecyl sulfate and diethyl ester can induce lecithine cleavage in the presence of Ca2+, while solid adsorbents, e.g. silicagel, can stimulate the reaction in the absence of Ca2+. The curve of the enzyme hydrolytic activity dependence on pH has two maxima, which depend on the type of the prime. Phospholipase D from radish roots, unlike the enzyme from other plants (cotton, peanut, cabbage, etc.) displays a more pronounced specificity for lecithine as substrate and is weakly active in the reaction with cephaline. Cephaline undergoes splitting by phospholipase D in the absence of Ca2+ as well, despite the fact that Ca2+ are necessary for lecithine hydrolysis. An addition of Ca2+ increases the enzymic affinity for the substrate in all cases studied. Some data on the transalkylating function of the enzyme are given.

Calcium↗