Discrimination between the regioisomeric 1,2- and 1,3-diacylglycerophosphocholines by phospholipases.

The artificial 1,3-diacyl-glycero-2-phosphocholines (1,3-PCs), which form similar aggregate structures as the naturally occurring 1,2-diacyl-sn-glycero-3-phosphocholines (1,2-PCs), were tested as substrates for different classes of phospholipases such as phospholipase A(2) (PLA(2)) from porcine pancreas, bee and snake venom, and Arabidopsis thaliana, phospholipase C (PLC) from Bacillus cereus, and phospholipase D (PLD) from cabbage and Streptomyces species. The regioisomers of the natural phospholipids were shown to bind to all investigated phospholipases with an affinity similar to the corresponding naturally occurring phospholipids, however their hydrolysis was reduced to different degrees (PLA(2)s and PLC) or even abolished (PLDs belonging to the PLD superfamily). The results are in accordance with binding models obtained by docking the substrates to the crystal structures or homology models of the phospholipases.

Zonal expression of hepatocytic marker enzymes during liver repopulation.

Hepatocytes are metabolically specialised cells displaying distinctive gene expression patterns within the liver lobule. Here, we investigate whether pre-cultured adult rat hepatocytes adopt periportal and pericentral enzyme expression following their transplantation into the regenerating rat liver. Isolated primary rat hepatocytes, representing a mixture of both periportal and pericentral origin, lost expression of carbamoyl phosphate synthetase I (CPS I) and cytochrome P450 subtype 2B1 (CYP2B1) in culture as shown by immunofluorescence and Western blot analysis.

Activity of phospholipase C in two-phase systems.

Although phospholipase C (PLC) is known to be activated by water-insoluble organic solvents, most activity assays have been designed to work in an aqueous milieu. Here a sensitive method is described for the determination of PLC activity in two-phase systems. The assay is based on the hydrolysis of phosphatidylcholine (PC) in chloroform/buffer.

1,3-Diacylglycero-2-phosphocholines--synthesis, aggregation behaviour and properties as inhibitors of phospholipase D.

A series of 1,3-diacylglycero-2-phosphocholines (1,3-PCs) with acyl chain lengths of C8-C18 were synthesised by chemical introduction of the phosphocholine moiety into the regioisomerically pure 1,3-diacylglycerols, which were obtained from glycerol and the vinyl esters of fatty acid by means of lipase from Rhizomucor mihei. The 1,3-PCs being regioisomers of the natural glycerophospholipids were studied with respect to their aggregation behaviour in the absence and in the presence of sodium dodecylsulfate (SDS) as well as their properties as substrates and inhibitors of phospholipase D (PLD) from cabbage. While the main structures of the pure 1,3-PCs were micelles (C8), liposomes (C10, C12) or planar bilayers (C14, C16, C18), the addition of SDS resulted in the formation of mixed micelles (C8, C10) and mixed liposomes (C12, C14, C16, C18).

Hexadecylphosphocholine and 2-modified 1,3-diacylglycerols as effectors of phospholipase D.

The kinetic behaviour of phospholipase D (PLD) from cabbage has been studied in the presence of several substrate-like compounds such as hexadecylphosphocholine (HPC) and 1,3-didodecanoylglycero-2-phosphatides. 1,3-Didodecanoyl- glycero-2-phosphocholine (1,3-DiC12PC) was found being not cleft by PLD, whereas HPC is hydrolyzed by PLD with small rate. The plot of initial velocity vs.

2-modified 1,3-diacylglycerols as new surfactants for the formation of reverse micelles.

New 2-modified 1,3-diacylglycerols such as 1,3-dilauroylglycerol 2-disodiumphosphate and analogues were characterized with respect to their tendency to form reverse micelles in isooctane and isooctane/1-hexanol. The water content of the reverse micelles was determined by Karl-Fischer titration. The critical micelle concentration of the compounds was estimated by fluorescence measurements using rhodamine B as indicator.