Biochemistry and Molecular Biology - Belyasova N.A. 2002

Metabolism. Processes Requiring Energy Input
Lipid Biosynthesis
Formation of Unsaturated Fatty Acids

Unsaturated Fatty acids are synthesized from saturated fatty acids of corresponding chain length. The Introduction of a double bond in aerobic organisms is catalyzed by the enzyme acyl-CoA oxygenase, with oxidation proceeding According to the reaction:

Class="center">Пальмитоил-СоА + NADPH + H⁺ + O₂ →

→ Пальмитолеил-СоА + NADP⁺ + 2 H₂O

In this process, two different substrates are oxidized simultaneously: the fatty acid (resulting in The formation of a double bond) and NADPH, catalyzed by Monooxygenases known as desaturases. Another mechanism for introducing double bonds into fatty acid molecules is also known, which does not require molecular oxygen. For instance, in E. coli Cells, the synthesis of palmitoleic acid begins right at the fatty acid synthase stage, starting with the formation of a double bond within a C₁₀ fragment. This reaction involves a specialized enzyme found in the bacterium—β-hydroxydecanoyl thioester dehydratase—which catalyzes the formation of a cis-β,γ-double bond rather than a trans-α,β-bond, as occurs during the Formation of the enoyl derivative in saturated fatty acid synthesis. Subsequently, the unsaturated fragment is elongated into C₁₆ and C₁₈ derivatives.

In animals and plants, the introduction of the first double bond into a saturated fatty acid molecule occurs quite readily in the Cytosol. The formation of additional double bonds takes place in The Endoplasmic reticulum in plants, whereas animals lack this capability entirely. Consequently, polyunsaturated fatty acids (such as linoleic and linolenic acids) are essential dietary components for animals, particularly mammals, and must be obtained from plant-based foods. These fatty acids serve as precursors for the Synthesis of Other polyunsaturated fatty acids. A deficiency of linoleic and linolenic acids in the animal diet leads to growth retardation, Skin and Kidney lesions, and reproductive disorders.