Hydrolysis of synthetic phosphatides by clostridium welchii phosphatidase

Dissociation of various biological activities of Clostridium perfringens alpha toxin by chemical modification

The effect of N-acetylimidazole, tetranitromethane, maleic anhydride and N-ethylmaleimide on various biological activities of Clostridium perfringens alpha (alpha)-toxin was investigated. Treatment of the toxin with N-acetylimidazole, tetranitromethane or maleic anhydride resulted in significant reduction of lethal, hemolytic and platelet-aggregating activities and phospholipase C activity (EY activity), as measured by increased turbidity in egg yolk emulsions. However, EY activity was more resistant to these reagents than lethal, hemolytic or aggregating activities. Phospholipase C activity (PN activity) as measured by hydrolysis of p-nitrophenylphosphorylcholine was retained after treatment with N-acetylimidazole, tetranitromethane or maleic anhydride. The activities of the toxin were not inactivated by treatment with N-ethylmaleimide. These data suggest that alpha-toxin contains multiple sites for biological activities of the toxin.

Cardiolipin-protein interactions in the phosphate binding activity of a proteolipid from yeast mitochondria. Action of phospholipases A2 and C and of cations

A proteolipid able to bind phosphate has been isolated from yeast mitochondria. During the purification the active protein was always associated with cardiolipin. The cardiolipin requirement for the phosphate binding activity of this proteolipid has been studied using controlled lipid depletion with two phospholipases A2 and with phospholipase C. Only phospholipase A2 from pig pancreas, that deacylated cardiolipin, promoted inhibition of the proteolipid activity (but never more than 70 per cent). Phospholipase A2 from snake venom did not inhibit the binding activity of the proteolipid. Using thin layer chromatography with two sequential solvents it was possible to separate two cardiolipin subspecies; one of them was preferentially hydrolysed by phospholipase C of Bacillus cereus, leading to inhibition of the proteolipid activity. Ca2+ complexed to cardiolipin stoichiometrically (1-1) inhibited the proteolipid activity. This effect could be due to a conformational change in the cardiolipin-protein association.

The dynamics of membrane structure

The membranes of living organisms are involved in many aspects of the life, growth and development of all cells. The predominant structural elements of these membranes are lipids and proteins and the basic strucvture of these molecules has been reviewed. The physical properties of the lipid constituents particularly their behavior in aqueous systems has led to the concepts of thermotropic and lyotropic mesomorphism; the interaction between different types of lipid molecules modulate this behavior. Interaction of phospholipids in aqueous systems with cholesterol, ions and drugs have been examined in this context. In addition a variety of model lipid-protein systems have been investigated and the implications of interactions between lipids and different proteins in biological membranes has been evaluated. This leads to a detailed consideration of the way lipids and proteins ae organized in cell membranes and contains an appraisal of the evidence supporting contemporary views of membrane structure. Particular attention has been devoted to the question of how mobile the components are within the structure. Particular attention has been devoted to the question of how mobile the components are within the structure. Finally the biosynthesis, turnover and modulation of the properties of interacting membrane constituents is critically reviewed and possible ways of controlling the behavior of cells and organisms by altering the structural parameters of different membranes has been considered.

Synthesis of choline and ethanolamine phospholipids with thiophosphoester bonds as substrates for phospholipase C

Spectrophotometric assays of esterases are sensitive, rapid, and quite specific when thioester substrates are used. Glycerophospholipids with thiophosphoester bonds may be useful as substrates for phospholipase C (EC 3.1.4.3). These have been made from mercaptoglycerol and mercaptoethanol. The thiols were oxidized to disulfides, acylated, and reduced with dithiothreitol. Phosphocholine derivatives were made by the classical methods for oxyphosphoesters. The phosphatidyl choline analogue was converted to the phosphatidyl ethanolamine analogue by transphosphatidylation with cabbage phospholipase D and ethanolamine. Structures were proved with enzymic hydrolysis, infrared spectra, TLC behavior, and elemental analyses. The synthesized compounds were rac-1-S-phosphocholine-2,3-O-didecanoyl-1-mercapto-2,3-propanediol, 1-S-phosphoethanolamine-2,3-O-didecanoyl-1-mercapto-2,3-propanediol, and 1-S-phosphocholine-2-O-hexadecanoyl-1-mercapto-2-ethanol.

Phospholipase C from Clostridium novyi type A. I

1. Phospholipase C (EC 3.1.4.3) from Clostridium novyi (oedematiens) type A was purified 2000-fold by (NH4)2SO4 precipitation, DEAE-Sephadex treatment in a batchwise system and Sephadex G-100 column chromatography. 2. The purified preparation had a specific activity of 95 mumol per min per mg protein toward phosphatidylcholine. This preparation was free from protease, lipase and oxygen-labile delta-hemolysin. 3. Phosphatidylcholine was hydrolyzed at the highest rate, while sphingomyelin and lysophosphatidylcholine were hydrolyzed at much lower rates. 4. Sodium deoxycholate and divalent cations such as Mg2+ and Ca2+ were extremely effective in stimulating phosphatidylcholine-hydrolyzing activity of this enzyme. 5. This enzyme hemolyzed horse red cells by hydrolyzing phosphatidylcholine, spingomyelin and phosphatidylethanolamine.

SYNTHESIS OF ENANTIOMERIC MIXED-ACID GLYCEROLPHOSPHATIDES: I. L-α-(α′-STEAROYL,β-OLEOYL)CEPHALIN AND L-α-(α′-OLEOYL,β-STEAROYL)CEPHALIN

α′-Stearoyl,β-oleoyl L-α-glycerylphosphorylethanolamine and α′-oleoyl,β-stearoyl L-α-glycerylphosphorylethanolamine were synthesized by phosphorylating D-α′-stearoyl,β-oleoylglycerol and D-α′-oleoyl,β-stearoylglycerol with phosphorus oxychloride and quinoline, esterifying the resulting mixed-acid phosphatidic acid dichlorides with 2′-hydroxyethylphthalimide in the presence of pyridine, and removing the protective phthaloyl group of the α′-stearoyl,β-oleoyl-, and α′-oleoyl,β-stearoyl-L-α-glycerylphosphoryl-2′-hydroxyethylphthalimides by hydrazinolysis.