Unsaturated fatty acids functions

Variants of this structure have one or more methyl substituents and encompass quite complex branched-chain fatty acids, which represent minor components in natural organisms, with the noteworthy exception of bacteria. The longest chain in branched-chain fatty acids defines the chain length of these compounds, such as the mycolic acids, which replace the unsaturated fatty acids functionally in Mycobacteria. 

Applications of peroxide formation are underrepresented in chiral synthetic chemistry, most likely owing to the limited stability of such intermediates. Lipoxygenases, as prototype biocatalysts for such reactions, display rather limited substrate specificity. However, interesting functionalizations at allylic positions of unsaturated fatty acids can be realized in high regio- and stereoselectivity, when the enzymatic oxidation is coupled to a chemical or enzymatic reduction process. While early work focused on derivatives of arachidonic acid chemical modifications to the carboxylate moiety are possible, provided that a sufficiently hydrophilic functionality remained. By means of this strategy, chiral diendiols are accessible after hydroperoxide reduction (Scheme 9.12) [103,104]. 

In the last decade numerous studies were dedicated to the study of biological role of nonenzymatic free radical oxidation of unsaturated fatty acids into isoprostanes. This task is exclusively difficult due to a huge number of these compounds (maybe many hundreds). Therefore, unfortunately, the study of several isoprostanes is not enough to make final conclusions even about their major functions. F2-isoprostanes were formed in plasma and LDL after the treatment with peroxyl radicals [98], It is interesting that their formation was observed only after endogenous ascorbate and ubiquinone-10 were exhausted, despite the presence of other antioxidants such as urate or a-tocopherol. LDL oxidation was followed by... 

Vitamin Ba (pyridoxine, pyridoxal, pyridoxamine) like nicotinic acid is a pyridine derivative. Its phosphorylated form is the coenzyme in enzymes that decarboxylate amino acids, e.g., tyrosine, arginine, glycine, glutamic acid, and dihydroxyphenylalanine. Vitamin B participates as coenzyme in various transaminations. It also functions in the conversion of tryptophan to nicotinic acid and amide. It is generally concerned with protein metabolism, e.g., the vitamin B8 requirement is increased in rats during increased protein intake. Vitamin B6 is also involved in the formation of unsaturated fatty acids. 

UV-induced ROS are extremely toxic to cells by causing oxidative damage to all biomolecules (Sies 1991). For instance, lipids, which are major compounds of all biological membranes, may be destroyed by ROS. After a first initiation reaction an unsaturated fatty acid is converted to a peroxyl radical, which in turn attacks another unsaturated fatty acid finally leading to free radical cascades. This photochemical peroxidation of unsaturated fatty acids may be particularly damaging for membrane structure and function (Bischof et al 2006a). 

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. ... 

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