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Steps in beta-oxidation of odd-numbered saturated fatty acids [15] For an odd-numbered saturated fat (C n ), 0.5 * n - 1.5 oxidations are necessary, and the final process yields 8 acetyl CoA and 1 propionyl CoA.
Acyl-CoA dehydrogenases (ACADs) are a class of enzymes that function to catalyze the initial step in each cycle of fatty acid β-oxidation in the mitochondria of cells.Their action results in the introduction of a trans double-bond between C2 (α) and C3 (β) of the acyl-CoA thioester substrate. [1]
[15] Breakdown of fatty acids by beta oxidation. In the cytosol of the cell (for example a muscle cell), the glycerol will be converted to glyceraldehyde 3-phosphate, which is an intermediate in the glycolysis, to get further oxidized and produce energy. However, the main steps of fatty acids catabolism occur in the mitochondria. [16]
After activation by ATP, once inside the mitochondria, the β-oxidation of a fatty acids occurs via four recurring steps: Oxidation by FAD; Hydration; Oxidation by NAD + Thiolysis; Production of acyl-CoA and acetyl-CoA; The final product of β-oxidation of an even-numbered fatty acid is acetyl-CoA, the entry molecule for the citric acid cycle. [3]
The two pathways are distinct, not only in where they occur, but also in the reactions that occur, and the substrates that are used. The two pathways are mutually inhibitory, preventing the acetyl-CoA produced by beta-oxidation from entering the synthetic pathway via the acetyl-CoA carboxylase reaction. [1]
Beta oxidation may begin now that Acyl-CoA is in the mitochondria. Beta oxidation of acyl-CoA occurs in four steps. 1. Acyl-CoA dehydrogenase catalyzes dehydrogenation of the acyl-CoA, creating a double bond between the alpha and beta carbons. [6] FAD is the hydrogen acceptor, yielding FADH2. [7] 2.
In mammals, this metabolic pathway is important in beta oxidation of fatty acids and catabolism of amino acids and choline, as it accepts electrons from multiple acetyl-CoA dehydrogenases. [32] [33] In plants, ETF-Q oxidoreductase is also important in the metabolic responses that allow survival in extended periods of darkness. [34]
Unlike the breakdown of saturated fat, cis and trans polyunsaturated fatty acid degradation requires three additional enzymes to generate a product compatible with the standard beta oxidation pathway. DECR is the second such enzyme (the others being enoyl CoA isomerase and dienoyl CoA isomerase) and