Fatty acids polyenoic

Eicosanoids These compounds, derived from eicosa- (20-carbon) polyenoic fatty acids, comprise the prostanoids, leukotrienes (LTs), and lipoxins (LXs). Prostanoids include prostaglandins (PGs), prostacyclins (PGIs), and thromboxanes (TXs). 

Certain long-chain unsaturated fatty acids of metabolic significance in mammals are shown in Figure 23-1. Other C20, C22, and C24 polyenoic fatty acids may be derived from oleic, linoleic, and a-flnolenic acids by chain elongation. Palmitoleic and oleic acids are not essential in the diet because the tissues can introduce a double bond at the position of a saturated fatty acid. 

Schnurr et al. [22] showed that rabbit 15-LOX oxidized beef heart submitochondrial particles to form phospholipid-bound hydroperoxy- and keto-polyenoic fatty acids and induced the oxidative modification of membrane proteins. It was also found that the total oxygen uptake significantly exceeded the formation of oxygenated polyenoic acids supposedly due to the formation of hydroxyl radicals by the reaction of ubiquinone with lipid 15-LOX-derived hydroperoxides. However, it is impossible to agree with this proposal because it is known for a long time [23] that quinones cannot catalyze the formation of hydroxyl radicals by the Fenton reaction. Oxidation of intracellular unsaturated acids (for example, linoleic and arachidonic acids) by lipoxygenases can be suppressed by fatty acid binding proteins [24]. 

The health impairing and toxic elfects of oxidation of lipids are due to loss of vitamins, polyenoic fatty acids, and other nutritionally essential components formation of radicals, hydroperoxides, aldehydes, epoxides, dimers, and polymers and participation of the secondary products in initiation of oxidation of proteins and in the Maillard reaction. Dilferent oxysterols have been shown in vitro and in vivo to have atherogenic, mutagenic, carcinogenic, angiotoxic, and cytotoxic properties, as well as the ability to inhibit cholesterol synthesis (Tai et ah, 1999 Wpsowicz, 2002). 

Smith et al. (1978) have described a procedure for the GLC determination of cis and trans isomers of unsaturated fatty acids in butter after fractionation of the saturated, monoenoic, dienoic, and polyenoic fatty acid methyl esters by argentation TLC. Total trans acids were much higher, as measured by infrared spectrophotometry than by GLC, probably because some of the acids could have two or more of the trans bonds designated as isolated by infrared spectrophotometry. Enzymatic evaluation of methylene-interrupted cis, cis double bonds by lipoxidase resulted in lower values than those obtained by GLC. The authors mention that the lipoxidase method is difficult, requiring considerable skill, and suggest that their method is suitable for the determination of the principal fatty acids in complex food lipids such as bovine milk fat. 

Normally, the method of choice for the analysis of complex mixtures of polyenoic fatty acids such as those derived from fish oils is capillary gas chromatography with prechromato-graphic derivatization and mass spectrometric detection. However, GC is impractical for the purification of the large amounts of polyenoic fatty acids required for biological and clinical studies. Moreover, the temperatures required in GC may cause degradation of oxidized long-chain polyunsaturated fatty acids that are present as minor components of the mixture. 

Polyenoic fatty acids (acids with more than one double bond in the chain) play a leading role where total unsaturation is observed to change. According to current concepts, the structure and functioning of cell membranes are maintained through the agency of a binary film composed of phospholipids and cholesterol. The phospholipids consist of polar, outwardly directed heads and fatty acid tails immersed in the membrane (Fox, 1972 Singer and Nicholson, 1972 Chapman, 1973). In this binary film, there are inclusions of protein molecules. 

On the other hand, some fish are able to synthesize long-chain polyenoic fatty acids (Kayama et al., 1963) from shorter carbon chains. Docosohexaenoic acid is laid down in coho salmon in quantities related to the size of the fish, rather than to its availability in the diet (Tinsley et al., 1973). Rainbow trout fed on 18 2 and 18 3 fatty acids can produce 20 3, 22 5 and 22 6 fatty acids in substantial quantities (Owen et al., 1975), but these workers noticed that the capacity of marine flatfish to elongate or desaturate the carbon chains was more limited. They found that 70% of the radioactivity of labelled 18 3 appeared later in the 22 6 fatty acid of rainbow trout, but that turbot converted only 3-15% of labelled precursors into polyunsaturated fatty acids of longer chain length. It was suggested that turbot in the wild probably received adequate polyunsaturated acids in their diet, which the fish therefore did not need to modify. The elongation of the carbon chains and the creation of more double bonds is also only slight in Atlantic cod, another marine teleost, presumably for the same reason (Ross, 1977). 

As mentioned earlier, the polyenoic fatty acids from marine fish are mostly from the linolenic series (m3). These are eicosopentaenoic (C20 5o>3) and docosohexaenoic (C22 6o>3) acids, the latter usually being the more abundant. Yakovleva (1969) reported that in Black Sea fish die ratio between fatty acids of the 3 and 6 series also displayed a close correlation with the natural mobility levels. 

In the past, the fish used as food for man or farm animals was evaluated on the basis of protein and total lipid content, but nowadays the emphasis is on the biologically active substances such as polyenoic fatty acids, vitamins and antioxidants. Recent problems have arisen because of contamination with sewage, mineral oil and its by-products, heavy metals and radioactive pollutants. The bizarre finding of certain Tasmanian oysters, bred downstream from a zinc smelting plant, which contained 10% of zinc on a dry weight basis is an... 

There are about 200 minor monoenoic, dienoic and polyenoic fatty acids in milk fat ranging in chain length from C10 to C24, and consisting of both positional and cisltrans isomers. A number have considerable nutritional significance for example, eicosapentaenoic acid (20 5,0.09%) and docosahex-aenoic acid (22 6,0.01%) are present in the metabolic pathway of the n-3 fatty acids, while arachidonic acid (20 4, 0.14%) is part of the n-6 pathway. 

Bhaskar, N.,Tomohisa, K., Miyashita, K., Park, S.-B., Endo, Y., and Fujimoto, K. 2004a. Occurrence of conjugated polyenoic fatty acids in seaweeds from the Indian Ocean. Z. Naturforsch., 59C. 310-314. 

Zheng, W., Wise, M. L., Wyrick, A., Metz, J. G., Yuan, L., and Gerwick, W. H. 2002. Polyenoic fatty acid isomerase from the marine alga Ptilota filicina protein characterization and functional expression of the cloned cDNA. Arch. Biochem. Biophys., 401,11-20. 

TABLE 12. Members of Polyenoic Fatty Acid Families. ... 

Table 2. Differences in Platelet Polyenoic Fatty Acids (<<>-6 and -3) and Bleeding Times Between (jreenland Eskimos and Danes ...

Naughton JM. Supply of polyenoic fatty acids to the mammahan brain the ease of conversion of the short chain essential fatty acids to their longer chain polyunsaturated metabolites in liver, brain, placenta and blood. Inti J Biochem 1980 13 21-32. 

Aveldano ML A novel group of very long chain polyenoic fatty acids in dipolyunsaturated phosphatidylcholines from vertebrate retina.. 1 Biol Chem 1987 262 1172-1179. 

Suh M, Wierzbicki AA, Clandinin MT. Dietary fat alters membrane composition in rod outer segments in normal and diabetic rats impact on content of very-long-chain (C>24) polyenoic fatty acids. Biochim Biophys Acta 1994 1214 54-62. 

The preparation and handling of the fluorescent phospholipid derivatives is cumbersome, however. Special care has to be taken to prevent degradation of the polyenoic fatty acid. Furthermore, most spectroscopic techniques require calibration to equate the spectral changes with the amount of lipid transfer. It is also important to know whether the rate of transfer of this and other fluorescent and spin-labeled phospholipids is comparable to the transfer rate of more physiological phospholipid molecules. 

Gerwick et al. (1997) described an enzyme from the red alga Ptilota filicina, which they named polyenoic fatty acid isomerase. The enzyme was capable of converting AEA into novel substances such as conjugated triene anandamide. Chapman (2000) described FAAH-like amidohydrolase... 

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