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Biomedical subjects

N M Litvinko

Publications and source records attributed to N M Litvinko.

14 recordsLinked to original sources
PubMed2002

Dynamics of formation of lysoforms on enzymatic hydrolysis of phosphatidylalkanols.

Hydrolysis of 1,2-dioleoyl-sn-glycero-3-phosphomethanol (DOPM), 1,2-dioleoyl-sn-glycero-3-phosphoethanol (DOPEt), 1,2-dioleoyl-sn-glycero-3-phosphoethyleneglycol (DOPEG), and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) catalyzed by phospholipase A2 (PLA2) from porcine pancreas was studied in single-component and binary model bilayer membranes (liposomes). The presence of anionic phosphatidylalkanols increases the rate of hydrolysis of zwitterionic DOPC in liposomes by the action of PLA2. The rate of formation of lysoforms of anionic ("acidic") lipids at the initial reaction stage in single-component liposomes increased in the following sequence: DOPEG < DOPM < DOPEt (compared with that for the zwitterionic DOPC). In binary liposomes formation of lyso-DOPC increased in the presence of acidic lipids in the following sequence: DOPM < DOPEt < DOPEG. This indicates that the size of polar fragment of the second substrate and the presence of free hydroxy groups in the "head" of DOPEG may possibly activate DOPC hydrolysis by the action of PLA2 in the presence of anionic phospholipids including cardiolipin; the studied phospholipids model fragments of the latter.

Alcohols↗
PubMed2001

Influence of ethanol and phosphatidylethanol on the activity of pancreatic phospholipase A2.

Hydrolysis of dioleoylphosphatidylethanol (DOPEt) and dioleoylphosphatidylcholine (DOPC) catalyzed by phospholipase A2 (PLA2) from porcine pancreas has been studied in single-component and binary liposomes in the absence and in the presence of ethanol. DOPEt (an anionic phospholipid) was found to increase the rate of hydrolysis of zwitterionic DOPC in liposomes under the action of PLA2.

Animals↗
PubMed1992

[Lipolysis in model membranes in the presence of positively charged soluble proteins].

Phospholipase A2 hydrolysis of neutral and negatively charged lipid membranes modified by positively charged proteins has been studied using liposomes composed of either dioleoylphosphatidylcholine (DOPC) or dioleoylphosphatidylglycerol (DOPG) alone or their equimolar mixture in the presence of cytochrome c, histone H1, cytochrome b5, and polylysine. Twenty minutes after the reaction had been initiated, DOPC hydrolysis was 58%, while that in the equimolar mixture with DOPG was 35%. DOPG hydrolysis was more complete in binary mixtures of liposomes. The same was observed for liposomes in the presence of cytochrome c. Hydrolysis of phospholipids in binary liposomes in the presence of histone H1 was 3 times faster than that in protein-free liposomes. In the presence of polylysine the rate of DOPG hydrolysis was decreased. The results obtained are suggestive of electrostatic interactions between hydrophilic proteins and negatively charged phospholipids, the phospholipase A2 catalytic activity being affected by these interactions.

Cytochrome c Group↗
PubMed1989

[Study of phospholipase A2 specificity in substrate-containing structures having different supramolecular organization].

The specificity of snake venom phospholipase A2(PLA2) towards a number of phospholipid (PL) substrates, e. g., phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) organized in Triton X-100 mixed micelles, liposomes and proteoliposomes was studied. PC was shown to be more rapidly hydrolyzed in micelles. For other PLs, the rate of hydrolysis decreased in the following sequence: PC greater than PI greater than PE greater than PG. The incorporation into micelles of a non-hydrolyzable by PLA2 sphinogomyelin which, similar to PC, has a choline group, resulted in an increase of PLA2 specificity towards PL that are known to be devoid of this group: PE greater than PI greater than PG greater than PC. Quite a different picture was observed in bilayer liposomal structures: PI congruent to PE greater than PC greater than PG. The incorporation of cytochrome P-450 into liposomes caused the acceleration of PE and PG hydrolysis. The course of the PLA2-catalyzed hydrolysis in model membrane structures seems to be governed primarily by the supramolecular organization and localization of the substrate in the bilayer, but not by its chemical structure.

Animals↗
PubMed1977

[The actions of low-molecular fragments of substrate and their analogs on the activity of isoenzymes of phospholipase C from Clostridium perfringens].

The interaction of the lecithin molecule fragments and their analogues with phospholipase C Cl. perfringens was studied by gel-diffusion in agarose-lecithin gels. It was found intense inhibition of phospholipase C activity in the presence of cathionic compounds; this phenomenon shows the existence of anionic centre in the active site of enzyme. The esteric centre is probably hydrophobic nature and is not capable to bind the negatively charged groups. However, phosphoserine, phosphothreonine, gamma-aminobutyric, aspartic and glutamic acids can interact with an additional cathionic centre, whose location in phospholipase C differs from that in pancreatic phospholipase A2.

Anions↗
PubMed1977

[Anionic center of porcine pancreatic phospholipase A2].

The interaction between porcine pancreatic phospholipase A2 and low-molecular fragments of its substrate -- lecithine was studied using gel-diffusion of the enzyme in lecithin-agarose plates. When the inhibitor was added, a decrease in the magnitude of cleared areas (l/l0) around the depots filled with enzyme solution was observed. A marked decrease in l/l0 in the presence of alpha- and beta-glycerophosphates supported the statement that the cathionic center is a part of the enzyme active site SII. The potent inhibition of phospholipase activity in the presence of phosphocholine, choline, acetylcholine, thiocholine and acylthiocholines suggests the existence of an anionic center SIII in the active site. This suggestion is supported by intensive inhibition of phospholipase activity by certain, aliphatic amines. It was shown that the center is spaced in the direction of the cathionic center. SII. The main contribution to the binding of the cathionic lecithin part ("head") with the anionic center SIII is probably provided by the ion-ionic interactions.

Animals↗
PubMedDate not supplied

[Effect of chemical compounds on phospholipase A2 activity].

A simple and convenient method of simultaneous determinations of effects of any set of chemical compounds on enzymatic hydrolysis of phospholipids by using the method of diffusion phospholipase A2 in a lecithin-agarose gel.

Animals↗
PubMedDate not supplied

[Separation and purification of isoenzymes of Clostridium perfringens phospholipase C].

The procedure for separation and purification of isoenzymes of phospholipase C from Clostridium perfringens (PLC) was developed. The procedure included primary concentration of culture liquid proteins and isoenzyme separtion on DEAE-cellulose during negative sorption of the major isoenzyme. Further purification of the isoenzymes was achieved by (NH4)2SO4 fractionation by Sephadex gel-filtration and isoelectric focusing. During polyacrylamide gel electrophoresis and precipitation reaction in the agar with the antiperfringens hyperimmune serum alpha1-PLC preparations were homogenous. Their coefficient of sedimentation was 3.8 S and isoelectric point was 5.50. The minor isoenzyme alpha2-PLC had the same coefficient of sedimentation and the isoelectric point of 5.35.

Clostridium perfringens↗
PubMedDate not supplied

[The use of hemoglobin for determination of phospholipase A2 activity].

A spectrophotometric method is proposed for determining phospholipase A2 activity, which is based on the conversion of hemoglobin into hemichrome under the fatty acid action. The spectral difference between hemoglobin and hemichrome was registered by the difference spectrum with a minimum at 405 nm and a maximum at 423 nm. The absorption value determined as the difference between the spectrum maximum and minimum was proportional to the amount of the fatty acid derived from hydrolysis of phospholipids. The method enables the enzyme activity to be determined directly in the spectrophotometric cell.

Hemoglobins↗
PubMedDate not supplied

[The resistance of liposomes as potential drug carriers to the action of phospholipase A2].

Stability of liposomes with varied phospholipid (PL) content towards the action of phospholipase A2 (PLA2) was studied in vitro. Liposomes were prepared of phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylinositol (PI) and their mixtures with sphingomyelin (SM). PC and PG liposomes were also treated with PLA2 in the presence of a number of proteins such as cytochrome c, cytochrome b5, cytochrome P-450, polylysine, and histone H1. Among all the liposomes studied PG-containing ones were found to be most stable towards PLA2. In SM-containing liposomes, the levels of PG, PI, PE and PC after 20 min of hydrolysis were 65, 62, 55 and 50%, respectively. In PC + PG liposomes, the PC content after treatment with PLA2 was by about 15-20% higher than in control PC liposomes. The addition of all the proteins studied influenced significantly stability of both PC and PG in two-component PL liposomes, but had no effect on liposomes consisting only of PC. The incorporation of the integral membrane protein cytochrome P-450 into PC and PG liposomes caused a decrease in their stability towards PLA2, the decrease depending on the lipid/protein molar ratio.

Drug Carriers↗
PubMedDate not supplied

[The phospholipase A2 hydrolysis of irradiated lipid membranes].

Phospholipase A2 hydrolysis of dioleoylphosphatidylcholine, dimyristoylphosphatidylcholine or their equimolar mixture with sphingomyelin in liposomes exposed to gamma-radiation has been investigated. Stabilization of the gamma-irradiated lipid bilayer to hydrolysis by sphingomyelin has been shown.

Free Radicals↗
PubMedDate not supplied

[Complex-formation of phospholipase A2 with fragments of nucleic acids and approaches to its elimination].

Formation of phospholipase A2 stable complexes with nucleic acid fragments was observed upon the isolation of the enzyme from pig pancreas. This complex could be disrupted by neither DNA precipitation with protamine chloride and cetyltrimethylammonium bromide nor chromatography on DEAE-cellulose and CM-cellulose or hydroxyapatite. The treatment of the complexes with 1 M acetic acid followed by gel-chromatography on Sephadex G-75 in 1 M acetic acid resulted in complete separation of active phospholipase A2 from DNA fragments.

Animals↗