Unsaturated fatty acids, families

Important essential fatty acids in the diet are linoleic acid (cis,cis-9,12-octadecadienoic acid, 18 2d9,12) and a-linolenic acid (all-cis-9,12,15-octadecatrienoic acid 18 3d9,12,15). The numbering in this conventional system begins with the carboxyl group. The "short hand," for example 18 2d9,12, indicates 18 carbon atoms, with two double bonds located between carbon atoms 9 and 10 and 12 and 13. There is an alternative system of numbering in which fatty acids are numbered from the methyl (or a>) terminal. In this case, linoleic acid is designated a>-6,9-octadecadienoic acid (18 2ft)6), and a-linolenic acid is o>-3,6,9-octadecatrienoic acid (18 3ft)3). This serves to designate two unsaturated fatty acid families, the ft)6 and the a families. 

FIGURE 10.2 Unsaturated fatty acid families and their importance in the formation of eicosanoids and long-chain PUPA (LCPUFA). 

Unsaturated fatty acids are probably the most abundant oxidizable endogenous substrates. In the past it was erroneously believed that unsaturated fatty acids are just products of lipid peroxidation. Now, it has been shown that they have dietary origin. Family of unsaturated fatty acids includes linoleic (Ci8), arachidonic (C2o), docosahexaenoic (C22), and other fatty acids containing two, three, four, five, or six double bonds. Some acids can be in vivo converted into others for example, linoleic acid can be metabolized to linolenic and eicosa-trienoic acids [78]. 

Prostaglandins are a subgroup of a larger family of compounds known collectively as eicosanoids, which are synthesized from arachidonic acid (arachidonate) this is a 20-carbon omega-6 unsaturated fatty acid (C20 4). The source of the arachidonic acid for PG synthesis is the cell membrane. Most membrane phospholipids have an unsaturated fatty acid as arachidonate at carbon 2 on the glycerol backbone to help maintain membrane fluidity. The arachidonic acid released from the membrane by the... 

The second family of secreted proteins that is covalently lipidated is the family of Wnt proteins. They are also involved in numerous processes like proliferation of stem cells, specification of the neural crest, and the expanding of specific cell types. The correct regulation of this pathway is important for animal development. Willert and coworkers were the first to isolate an active Wnt molecule. Mass spectroscopy studies carried out with the isolated protein revealed that cysteine 93 is palmitoylated. Mutating this amino acid to alanine led to almost complete loss of the signaling activity. Later in 2006, a second lipidation was found on a serine in Wnt3a. " In this case, the hydroxyl side chain is acylated with palmitoleic acid. This unsaturated fatty acid seems to be crucial for the progression of the protein through the secretory pathway. The attachment of two different lipid chains may therefore serve different functions. ... 

The omega (<0) numbering system is also used for unsaturated fatty acids. The co-family describes the position of the last double bond relative to the end of the chain. The omega designation identifies the major precursor fatty add, e.g., arachidonic add is formed from linoleic acid (co-6 family). Arachidonic acid is itself an important precursor for prostaglandins, thromboxanes, and leukotrienes. 

Three major families of unsaturated fatty acids are seen in warm-blooded animals, that is, the n-9, monounsaturated fatty acids (e.g. oleic acid, OA), and the n-6 and n-3, both polyunsaturated fatty acids (PUFAs). However, only the n-6 and n-3 families, derived from LA and ALA, respectively, are EFA. These must be obtained from the diet since mammals lack the desaturase enzymes necessary for the insertion of a double bond in the n-6 and n-3 positions of the fatty acid carbon chain. Fatty acid nomenclature is as follows The first number denotes the number of carbon atoms in the acyl chain and the second refers to the number of unsaturated (double) bonds. This is followed by a symbol n or co and a number that denotes the number of carbon atoms from the methyl terminal of the molecule to the first double bond. Hence, LA is 18 2(n-6), while the more unsaturated ALA is denoted as 18 3(n-3) (Figure 26.1). These fatty acids must be metabolized to their longer chain derivatives before carrying out many of their activities. 

Canola Oil occurs as a light yellow oil. It is typically obtained by a combination of mechanical expression followed by n-hexane extraction, from the seed of the plants Brassica juncea, Brassica napus, or Brassica rapa of the family Cruciferae. The plant varieties are those producing oil-bearing seeds with a low erucic acid (C22 i) content. It is a mixture of triglycerides composed of both saturated and unsaturated fatty acids. It is refined, bleached, and deodorized to substantially remove free fatty acids phospholipids color odor and flavor components and miscellaneous, other non-oil materials. It can be hydrogenated to reduce the level of unsaturated fatty acids for functional purposes in foods. It is a liquid at 0° and above. 

Rose, Rosa canina L., also known as dogberry or hop fruit, is in the Rosaceae family. The fruit of this particular species of rose is generally used to prepare a stew. The seeds from Rosa canina L. were investigated for their chemical composition and nutritional values for medicinal purposes. Seed oils were prepared from fruits grown at three locations in Turkey and evaluated for their fatty acid composition (31). Linoleic acid was the primary fatty acid detected, which ranged from 48.6-54.4% of total fatty acids, followed by a-linolenic acid (16.4-18.4%) and oleic acid (14.7-18.4%) (Table 4). The seed oil contained approximately 85% total unsaturated fatty acids, indicating that Rosa canina L. seed oil may be an excellent source for unsaturated and essential fatty acids. 

Several pharmacologically active substances are present in superfusates of the cerebral cortex, including acetylcholine, 5-hydroxytryptamine, substance P and the prostaglandins. Members of this latter family of hydroxy-unsaturated fatty acids are released from a great variety of tissues on nerve and hormone stimulation (Ramwell and Shaw 1970), and have been shown to possess a wide range of biological activity (Horton, 1969). 

Wnt proteins are also acylated. The Wnt3a protein is modified by thioester-linked palmitate at a conserved cysteine residue and also by an unsaturated fatty acid, palmitole-ic acid, which is oxyester-linked to a conserved serine residue (R. Takada, 2006). Porcupine (pore), a member of the MBOAT family, is required for the O-acylation of Wnt3a. It is not clear whether pore or another acyltransferase carries out the 5-acyl modification. 

The defense mechanisms of G. vermiculophylla seem to involve the arachidonic acid pathway that can lead to prostaglandins and hydroxylated unsaturated fatty acid, such as members of the HETE family. Addition of H-labeled arachidonic add to wounded alga showed that labeled fatty acids were generated rapidly. Interestingly, these results suggested that the enzymatic processes necessary for the activation of the defense mechanism remained viable, despite the damage to the tissues. The metabolomic assay used validated the existence of the chanical defenses and characterized the mechanisms and biochemical pathways involved. 

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