Membrane lipids fatty acids

EFFECTS OF ALLELOCHEMICALS ON ALGAL PLASMA MEMBRANE LIPID FATTY ACIDS... 

These and related experiments suggest a mechanism for the control of membrane lipid fatty acid composition. 

In our previous research, we found that the antialgal allelochemical Ethyl 2-Methylacetoacetate (EMA) caused loss of cell membrane integrity. It hinted that EMA may cause a change in the membrane. It is reported that environmental stress may increase the concentration of ROS in plant cell. The excessive ROS may cause a decrease of antioxidation enzymes activity and lipid peroxidation. The effect of EMA on the activity of SOD and POD and lipid fatty acids of Chlorella pyrenoidosa, Chlorella vulagaris and Microcystis aeruginosa were evaluated to elucidate the mode of action of EMA. 

Oxidative damage to membrane polyunsaturated fatty acids leads to the formation of numerous lipid peroxidation products, some of which can be measured as index of oxidative stress, including hydrocarbons, aldehydes, alcohols, ketones, and short carboxylic acids. 

Lipids encompass a wide class of amphiphilic molecules which, along with proteins, form the biological membranes necessary to support cellular function. While the simplest lipids, fatty acids and triglycerides, are not... 

Together with proteins, phospholipids are the most important structural components of biological membranes. Since mobility of the lipid segments fa vors molecular transport through a membrane and thereby increases its permeability, a marked increase in 7] along a lipid-fatty acid chain also reflects a more efficient molecular diffusion through the lipid layer of a membrane [175]. 

Biosynthesis of carbohydrates, fatty acids Biosynthesis of membrane lipids, amino acids Nutrition and digestion Immune systems, antigens... 

Very-Low-Density Lipoproteins (VLDL) are less dense than chylomicrons. They contain more protein, although lipids (fatty acids, cholesterol and phospholipid, in that order) still make up 90 to 95 percent of their weight. Low-density lipoproteins (LDLs) are about 85 percent lipid by weight and contain more cholesterol than any other kind of lipid. VLDL and LDL contain large amounts of Apolipoprotein B. The VLDL and LDL are sometimes referred to as bad cholesterol because elevated serum concentrations of these lipoproteins correspond with a high incidence of artery disease (stroke and heart disease). The LDLs carry cholesterol and fatty acids to sites of cellular membrane synthesis. 

Such imbalanced antioxidant systems in schizophrenia could lead to oxidative stress- and ROS-mediated injury as supported by increased lipid peroxidation products and reduced membrane polyunsaturated fatty acids (PUFAs). Decrease in membrane phospholipids in blood cells of psychotic patients (Keshavan et al., 1993 Reddy et al., 2004) and fibroblasts from drug-naive patients (Mahadik et al., 1994) as well as in postmortem brains (Horrobin et al., 1991) have indeed been reported. It has also been suggested that peripheral membrane anomalies correlate with abnormal central phospholipid metabolism in first-episode and chronic schizophrenia patients (Pettegrewet al., 1991 Yao et al., 2002). Recently, a microarray and proteomic study on postmortem brain showed anomalies of mitochondrial function and oxidative stress pathways in schizophrenia (Prabakaran et al., 2004). Mitochondrial dysfunction in schizophrenia has also been observed by Ben-Shachar (2002) and Altar et al. (2005). As main ROS producers, mitochondria are particularly susceptible to oxidative damage. Thus, a deficit in glutathione (GSH) or immobilization stress induce greater increase in lipid peroxidation and protein oxidation in mitochondrial rather than in cytosolic fractions of cerebral cortex (Liu et al., 1996). 

Incorporation of ruptured erythrocytes into the incubation system, at equimolar concentrations of oxyhaemoglobin to 15-HPETE, extensively protected the membrane polyunsaturated fatty acids from lipid peroxidation... 

The FABPs are a family of carrier proteins for fatty acids and other lipophilic substances, such as eicosanoids and retinoids. These proteins are thought to facilitate the transfer of fatty acids between extra- and intracellular membranes. Adipocyte fatty acid-binding protein (aP2 FABP4) is expressed in adipocytes and macrophages, and integrates inflammatory and metabolic responses. Studies in aP2-deflcient mice have shown that this lipid chaperone has a significant role in several aspects of the metabolic syndrome, including type 2 diabetes and atherosclerosis. FABP has also been introduced as a plasma marker of acute myocardial infarction. 

The leaves of higher plants contain upto 7% of their dry weight as fats some of which are present as surface lipids, the others as components of leaf cells, especially in the chloroplast membrane. The fatty acid composition of plant membrane lipids is very simple. Six fatty acids- palmitic, palmitoleic, stearic, oleic, linoleic and y-linolenic generally account for over 90% of the total fatty acids. 

Tlie polar head group of the molecule regulates the overall charge and hydrophilicity of the membrane. The major polar groups in biomembranes may be choline, ethanolamine, serine, inositol, galactose or in some cases n-acetylneuraminic acid. The non-polar acyl-chains influence greatly the fluidity and the packing of the membrane. Saturated fatty acid residues while decrease the fluidity and produce more compact membranes, unsatiirated acyi-chains increase the fluidity and minimize the lipid orientation of the membrane. 

The mechanism of carbon tetrachloride nephrotoxicity involves the initial homolytic cleavage of carbon tetrachloride by cytochrome P450 to form the trichloromethyl and chlorine free radicals (Figure 6). The trichloromethyl free radical can then alkylate renal macromolecules or interact with membrane unsaturated fatty acids to initiate lipid peroxidation. The trichloromethyl free radical may also combine with molecular oxygen to form a peroxy free radical that is more reactive than the trichloromethyl free... 

Phospholipids are asymmetrically distributed in the lipid bilayer, with phosphatidylethanolamine predominating on the matrix side and phosphatidylcholine on the cytoplasmic side. Seventy-five percent of the cardiolipin is present on the matrix side of the membrane. The fatty acid composition of the phospholipids depends on the species, tissue, and diet. In all cases, sufficient unsaturated fatty acids are contained in the phospholipids to provide a highly fluid membrane at physiological temperatures. 

GPI anchors may provide subtle functions, such as influencing the overall characteristics of the cell membrane. The fatty acid content of the anchor contributes to the lipid composition of the membrane and can determine the membrane packing characteristics of the protein. Membrane-anchored proteins that do not require transmembrane or cytoplasmic domains will, by default, reduce protein clutter by not interfering with other molecules in these regions [8,20]. 

Fatty acids enter cells both by a saturable transport process and by diffusion through the lipid plasma membrane. A fatty acid binding protein in the plasma membrane facilitates transport. An additional fatty acid binding protein binds the fatty acid intracellularly and may facilitate its transport to the mitochondrion. The free fatty acid concentration in cells is, therefore, extremely low. 

---