Diol lipids of rat liver. Quantitation and structural characteristics of neutral lipids and phospholipids derived from ethanediol, propanediols, and butanediols

Palmitoyl diol S- and O-phosphoroamidates of some sterols

The hexamethylphosphorus triamide activated by the addition of iodine at the optimum molar ratio 1.05:0.05 was used as a phosphorylating reagent to synthesize 1-palmitoyloxyethyl-2-O-, 1-palmitoyloxypropyl-3-O- and 1-palmitoyloxybutyl-4-O-(N,N-dimethylamido)thiophosphate and -phosphate derivatives of beta-sitosterol, cholesterol and stigmasterol in a one-pot procedure with overall yields of 80-87%. 1-Palmitoyloxypropyl-3-O-(cholesteryl-3-O)-(N,N-dimethylamido++ +) phosphite was used as a model synthon for the preparation of transamidated morpholido-thiophosphate and -phosphate analogues with final yields of 82-86%.

Synthesis of 1-O-acylethane-2-O-amidothionphosphates and their R,S-alpha-tocopherol derivatives as a new model type of phospholipids

The 1-O-acylethane-2-O-bis(N,N-diethylamido)- and 1-O-acylethane-2-O-(R,S-alpha-tocopheryl-6-O-)-(N,N- diethylamido)-thionphosphate derivatives of stearic acid, oleic acid and linoleic acid have been synthesized as new model phospholipid structures.

Modulation of diacylglycerol acyltransferase by lysophosphatidylcholine and related monochain phospholipids

Acyl-CoA : 1,2-diacylglycerol O-acyltransferase (EC 2.3.1.20) activity of rat liver microsomes was found to be stimulated by 1-acyl-sn-glycero-3-phosphocholine at low concentrations, but was inhibited above 0.2 mM. Diacylglycerol acylation was optimal at 75 microM lysophosphatidylcholine, resulting in a more than 2-fold activation of the enzyme. Acyltransferase activity disappeared above 0.5 mM lysophosphatidylcholine levels. 0.05% sodium taurocholate supplementation reduced diacylglycerol acyltransferase activity by approx. 2/3 over the entire range of lysophosphatidylcholine concentrations. 1-O-Hexadecylpropanediol-3-phosphocholine was shown to mimic lysophosphatidylcholine at stimulatory and at inhibitory concentrations in the absence and in the presence of sodium taurocholate, thus ruling out acyl-CoA depletion due to lysophosphatidylcholine acylation as a cause of depressed triacylglycerol synthesis at higher lysophosphatidylcholine levels. 1-Acyl-sn-glycero-3-phosphoethanolamine stimulated diacylglycerol acyltransferase to a lesser extent, without showing inhibition at higher concentrations. The data point towards a direct effect of the lysophospholipids on the acyltransferase system.

Ethanediol monoester hydrolysis by monoacylglycerol lipase of rat liver microsomes

The hydrolysis of long-chain monoester of ethanediol by rat,liver subcellular fractions was investigated in order to define the carboxylic acid ester hydrolase involved and to localize the enzymic activity. We found that with 1-O-hexadecanoyl [U-14C]ethanediol as substrate, hydrolytic activity was foremost associated with the rough microsomal fraction. The pH optimum occurred at 8.5. The apparent Km and V values were 6.5 . 10(-4) M and 13 mumol/h per mg microsomal protein, respectively. Enzymic activity was inhibited by p-chloromercuribenzoate and by diisopropylfluorophosphate, whereas NaF was less effective and CaCl2 did not affect apparent activity. Amongst a number of carboxylic acid esters tested as substrate, only long-chain 1-acyl and 2-acyl glycerols inhibited acyl diol hydrolysis competitively (Ki approximately 0.9 mM). It was concluded that long-chain monoesters of ethanediol are hydrolyzed by the monoacyl glycerol lipase system associated with the rat liver microsomal fraction. Because diol monoester is also utilized by the cholinephosphotransferase system of liver to form highly lytic acyl diol phosphocholines, efficient diol monoester hydrolysis by monoglyceride lipase may be a significant step in regulating acyl diol phosphocholine levels in biological systems.

Inhibition of diacylglycerol:CDPcholine cholinephosphotransferase activity by dimethylaminoethyl p-chlorophenoxyacetate

Cholinephosphotransferase [EC 2.7.8.2] activity of rat liver microsomes, with 1,2-di-0-[3H]acyl glycerol or 1-0-hexadecanoyl [U-14C]ethanediol as substrate, was inhibited by N,N-dimethylaminoethyl p-chlorophenoxyacetate (centrophenoxine). Inhibition progressed in a linear fashion with increasing drug levels and was complete at 30 mM concentration. It appears that the microsomal enzyme was largely affected by the drug itself because the hydrolysis products of centrophenoxine, viz., N,N-dimethylaminoethanol and p-chlorophenoxyacetic acid, were less inhibitory.