Fatty acids, from lipids

Table 2-18 Triglycerides and Phospholipids of Mackerel Lipids and Calculated Iodine Values for Methyl Esters of Fatty Acid from Lipids...

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... 

Lipases are enzymes that hydrolyze fatty acids from lipid species (e.g., triacylglycerols or phospholipids) in vivo. A number of lipases, mainly of bacterial origin, are now available immobilized onto a solid support for use as industrial scale catalysts. 

D. Metabolism of fatty acids from lipid storage depots releasing heat... 

Some bacteria, such as Haemophilus influenzae and N. meningitidis, express R-type LPS comprising a heterogeneous mixture of core oligosaccharides. LPS can be subjected either to O-deacylation to remove O-linked fatty acids from lipid A or to mild acid treatment to release the entire lipid A. These treatments increase the solubility for MS analysis and simplify the MS data for the elucidation of the structure of molecules. 

Lipid oxidation is an important topic in food science and technology since the reaction of polyunsaturated fatty acids with oxygen leads to rancidity and quality loss. The same process is important in human health, since the polyunsaturated fatty acids from lipids present in blood plasma (low density lipoproteins, LDL) are oxidised by oxygen in a free radical mediated reaction, promoting the development of atherosclerosis. LDL enters the arterial wall from the plasma and is oxidised locally within the wall by oxidising agents derived from the cells present in atherosclerotic... 

Metabolism of triacylglycerols in animals requires the interaction of lipoprotein lipase (involved in uptake of acyl chains from plasma) and hormone-sensitive lipase (involved in release of fatty acids from lipid stores). Some aspects of lipoprotein lipase action are discussed in Section 12.3 and the reader is also referred to Brockerhoff and Jensen (1974) and Jensen (1971). The enzyme is also known as clearing factor lipase, requires apo-Cn for activity and may be bound via heparan sulphate proteoglycan at the endothelial surface in vivo (Williams et aly 1983). Considerable work has been carried out on intracellular processing of the enzyme in active tissues (Cryer, 1981) and on the action of hormones in controlling the adipose and heart tissue enzymes (Ashby and Robinson, 1980 de Gasquet etaL, 1975). 

Parfene et al. (2013) also demonstrated the possibility to obtain food biopreservation as an effect of saturated fatty acids released from vegetal fats (coconut, palm and shea), by in situ sohd state cultivation of Yarrowia lypolitica selected strains. There was studied the fatty acids production in restrictive environmental conditions, similarly with those applied for food preservation, i.e., at low temperature (4°C) and reduced level of water activity (a 0.93). The gradual release of fatty acids from lipids was demonstrated in very simple experimental conditions. These results developed new concepts in food preservation as a consequence of using natural preservatives, without influencing the sensorial and nutritive characteristics thus having a great impact on spoilage control and food safety assurance. 

Jiittner, F. (2001) Liberation of 5,8,11,14,17-eicosapentaenoic acid and other polyimsaturated fatty acids from lipids as a grazer defense reaction in epilithic diatom biofilm. /. Phycol, 37, 744—755. 

Figure 17.2 Lipid peroxidation scheme. LH, a polyunsaturated fatty acid LOOM, lipid hydroperoxide LOH, lipid alcohol L, lipid radical LOO, lipid hydroperoxyl radical LO, lipid alkoxyl radical. Initiation the LH hydrogen is abstracted by reactive oxygen (e.g. lipid alkyl radical, lipid alkoxy radical, lipid hydroperoxyl radical, hydroxy radical, etc.) to produce a new lipid alkyl radical, L. Propagation the lipid alkyl, alkoxyl or hydroperoxyl radical abstracts hydrogen from the neighbouring LH to generate a new L radical.

Thioesters play a paramount biochemical role in the metabolism of fatty acids and lipids. Indeed, fatty acyl-coenzyme A thioesters are pivotal in fatty acid anabolism and catabolism, in protein acylation, and in the synthesis of triacylglycerols, phospholipids and cholesterol esters [145], It is in these reactions that the peculiar reactivity of thioesters is of such significance. Many hydrolases, and mainly mitochondrial thiolester hydrolases (EC 3.1.2), are able to cleave thioesters. In addition, cholinesterases and carboxylesterases show some activity, but this is not a constant property of these enzymes since, for example, carboxylesterases from human monocytes were found to be inactive toward some endogenous thioesters [35] [146], In contrast, allococaine benzoyl thioester was found to be a good substrate of pig liver esterase, human and mouse butyrylcholinesterase, and mouse acetylcholinesterase [147],... 

An extract of secretion from the sebaceous glands on head and neck of sexually active feral billygoats increases the number of does ovulating. The extract was placed on cotton wool and worn in facemasks. 4-Ethyloctanoic acid and 4-methyloctanoic acid, responsible for the goaty odor, were not active but both the free fatty acid and lipid-free non-acid fractions were. The 4-ethyl branched fatty acids are present in the active fraction (Birch etal., 1989). 

Lipid metabolism. The liver synthesizes fatty acids from acetate units. The fatty acids formed are then used to synthesize fats and phospholipids, which are released into the blood in the form of lipoproteins. The liver s special ability to convert fatty acids into ketone bodies and to release these again is also important (see p. 312). 

Lipid metabolism in the liver is closely linked to the carbohydrate and amino acid metabolism. When there is a good supply of nutrients in the resorptive (wellfed) state (see p. 308), the liver converts glucose via acetyl CoA into fatty acids. The liver can also take up fatty acids from chylomicrons, which are supplied by the intestine, or from fatty acid-albumin complexes (see p. 162). Fatty acids from both sources are converted into fats and phospholipids. Together with apoproteins, they are packed into very-low-density lipoproteins (VLDLs see p.278) and then released into the blood by exocytosis. The VLDLs supply extrahepatic tissue, particularly adipose tissue and muscle. 

Fatty acid hydroperoxides can be separated from each other and other lipids by MEKC followed by FLD according to equation 34 with 106a, using as catalyst microperoxidase-11 immobilized on the wall of a small capillary coupled at the end of the electrophoresis track. MEKC with DA-UVD can be applied for separation of unsaturated fatty acids from the mixture of hydroperoxides obtained on oxidation with 102 . ... 

CN213 Roche, M. E., and R. M. Clark. Lymphatic fatty acids from rats fed human milk and formula containing coconut oil. Lipids. 1994 29(6) 437-439. 

Among the different roles previously described, the liver exerts an excretory function, being involved in the formation of bile, which drains into the small intestine. Bile salts in the bile play an important role as emulsifying agents for the reabsorption of lipids and fatty acids from the intestine. Hepatic and obstructive biliary diseases lead to abnormal metabolism of bile acids (BAs). 

Lipid hydroperoxides can be removed by reaction with GSH catalyzed by GSH peroxidase. The enzyme phospholipase A2 has been proposed to have a role in the detoxication of phospholipid hydroperoxides by releasing fatty acids from peroxidized membranes. 

Certain classes of lipids are susceptible to degradation under specific conditions. For example, all ester-linked fatty acids in triacylglycerols, phospholipids, and sterol esters are released by mild acid or alkaline treatment, and somewhat harsher hydrolysis conditions release amide-bound fatty acids from sphingolipids. Enzymes that specifically hydrolyze certain lipids are also useful in the determination of lipid structure. Phospholipases A, C, and D (Fig. 10-15) each split particular bonds in phospholipids and yield products with characteristic solubilities and chromatographic behaviors. Phospholipase C, for example, releases a water-soluble phosphoryl alcohol (such as phosphocholine from phosphatidylcholine) and a chloroform-soluble diacylglycerol, each of which can be characterized separately to determine the structure of the intact phospholipid. The combination of specific hydrolysis with characterization of the products by thin-layer, gas-liquid, or high-performance liquid chromatography often allows determination of a lipid structure. 

Much of the cholesterol synthesis in vertebrates takes place in the liver. A small fraction of the cholesterol made there is incorporated into the membranes of he-patocytes, but most of it is exported in one of three forms biliary cholesterol, bile acids, or cholesteryl esters. Bile acids and their salts are relatively hydrophilic cholesterol derivatives that are synthesized in the liver and aid in lipid digestion (see Fig. 17-1). Cholesteryl esters are formed in the liver through the action of acyl-CoA-cholesterol acyl transferase (ACAT). This enzyme catalyzes the transfer of a fatty acid from coenzyme A to the hydroxyl group of cholesterol (Fig. 21-38), converting the cholesterol to a more hydrophobic form. Cholesteryl esters are transported in secreted lipoprotein particles to other tissues that use cholesterol, or they are stored in the liver. 

When the diet contains more fatty acids than are needed immediately as fuel, they are converted to triacylglycerols in the liver and packaged with specific apolipoproteins into very-low-density lipoprotein (VLDL). Excess carbohydrate in the diet can also be converted to triacylglycerols in the liver and exported as VLDLs (Fig. 21-40a). In addition to triacylglycerols, VLDLs contain some cholesterol and cholesteryl esters, as well as apoB-100, apoC-I, apoC-II, apoC-III, and apo-E (Table 21-3). These lipoproteins are transported in the blood from the liver to muscle and adipose tissue, where activation of lipoprotein lipase by apoC-II causes the release of free fatty acids from the VLDL triacylglycerols. Adipocytes take up these fatty acids, reconvert them to triacylglycerols, and store the products in intracellular lipid droplets myocytes, in contrast, primarily oxidize the fatty acids to supply energy. Most VLDL remnants are removed from the circulation by hepatocytes. The uptake, like that for chylomicrons, is... 

Increased synthesis of fatty acids De novo synthesis of fatty acids from acetyl CoA in adipose tissue is nearly undetectable in humans, except when refeeding a previously fasted individual. At other times, fatty acid synthesis in adipose tissue is not a major pathway (see Figure 24.5, G). Instead, most of the fatty acids added to the lipid stores of adipocytes are provided by dietary fat (in the form of chylomicrons), with a lesser amount is supplied by VLDL from the liver (see p. 229). 

Fatty acids are carried to tissues for use in synthesis of triacylglycerols, phospholipids, and other membrane lipids. The mobilization of fatty acids from triacylglycerol stores and from cholesterol esters depends upon hormone-sensitive lipase (p. 635).53b/ 53c This enzyme is activated by cAMP-dependent phos-... 

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