The synthesis of phosphatidylethanolamine and phosphatidylserine containing acetylenic or cyclopropane fatty acids and the activity of these phosphatides in blood coagulation

Effect of the fluorination degree of hydrophobic chains on the monolayer behavior of unsaturated diacylphosphatidylcholines bearing partially fluorinated 9-octadecynoyl (stearoloyl) groups at the air-water interface

The effect of the fluorination degree of hydrophobic chains on the monolayer behavior of unsaturated diacylphosphatidylcholines (PCs) was examined by employing a series of PCs bearing partially fluorinated 9-octadecynoyl (stearoloyl) groups (DFnStPCs, n: the number of fluorinated carbon atoms in a stearoloyl group; n=1, 2, 4, 8), including their hydrophobic parts--partially fluorinated stearolic acids (FnStAs)--at the air-water interface. π-A isotherm measurements and Brewster angle microscope observations revealed: (i) all DFnStPCs including FnStAs form monolayers of liquid character at 25 °C; (ii) they form more expanded monolayers than their non-fluorinated counterparts, distearoloyl-PC (DStPC) and stearolic acid, while the monolayer stability increases with n; (iii) compared with DStPC and DF8StPC, DFnStPCs (n=1, 2, 4) in the low-π region tend to show a weakening in their self-aggregation property and an increase in the work required for monolayer compression; (iv) although DF8StPC forms the most expanded monolayer, the behavior of DF8StPC resembles that of DStPC rather than that of DFnStPCs (n=1, 2, 4). The monolayer behavior of DFnStPCs (n=1, 2, 4) is explained by postulating a flatly-lying conformation of hydrophobic chains, in which three polar parts (ester group, triple bond, CF2-CH2 linkage) in chains are immersed in the subphase at large areas. DStPC and DF8StPC lacking a CF2-CH2 linkage, however, do not likely adopt such a conformation.

Kinetic evaluation of conversion of phosphatidylcholine to phosphatidylethanolamine by phospholipase D from different sources

Transphosphatidylation from phosphatidylcholine (PC) to phosphatidylethanolamine (PE) was conducted by seven phospholipase D preparations from different sources, one of which was of cabbage origin and other six of Streptomyces origin. The reactions were carried out at 30 degrees C using mixture of ethyl acetate containing PC and buffer containing ethanolamine and phospholipase D. To obtain the activity ratio of transphosphatidylation and hydrolysis at various ratios of ethanolamine and water concentrations, the apparent rate constant ratios of transphosphatidylation and hydrolysis, (k'3/k3)app, were calculated, keeping the concentration of PC constant (17.8 mM). Among the seven enzymes examined, five showed good transphosphatidylation, in which 100% of PC could be converted to PE at ethanolamine concentrations ranging from 0.3 to 1.0 M, while two showed poor transphosphatidylation activity. At higher ethanolamine concentrations, the reaction rate was decreased due to substrate inhibition. Hydrolytic reactions were conducted at 30 degrees C with respective enzymes by using mixture of ethyl acetate containing PC or PE and buffer containing phospholipase D. The ratio of (kcat/Km)PE/(kcat/Km)PC was calculated to determine the substrate specificity of various phospholipase D enzymes. The values of (k'3/k3)app varied with the origin of the enzymes, whereas the values of (kcat/Km)PE/(kcat/Km)PC were not so different. The results obtained show that (k'3/k3)app is a good parameter to select an enzyme and that the timing of stopping the reaction is also important to avoid the hydrolysis of the product.

Synthesis of glycerophospholipids

Recent advances in the synthesis of phosphatidic acids, phosphatidylethanolamines and phosphatidylcholines are described. Methods for the synthesis of some alkylacyl and alk-1-enylacyl analogues of the common diacylglycerophospholipids are also discussed. In addition, synthetic routes are described, that lead to unusual phospholipids such as compounds containing the polar group at position 2 of the glycerol moiety, glycerophospholipids containing alkanolamines of different chain lengths, and glycolphospholipids. All of the common glycerophospholipids can be prepared without the use of protecting groups. Major advances in phospholipid synthesis involve the application of novel phosphorylating agents and the use of cyclic intermediates. Although phosphatidylserines and phosphatidylthreonines as well as phosphatidylglycerols and cardiolipins can be prepared by chemical synthesis, further systematic studies are required to work out procedures that lead to these compounds in high yields.