Biochemistry - The Chemical Reactions of Living Cells, Volume 2 - D. Metzler 1980

Organization of Metabolism: Catabolic Pathways
Fatty Acid Oxidation
Oxidation of Unsaturated Fatty Acids

The β-oxidation of unsaturated acids, such as ∆9-oleic acid, yields ∆3-cis-enoyl-CoA as an intermediate. The oxidation process can proceed further only upon the action of a specific ∆3-cis-∆2-trans-enoyl-CoA isomerase [1] [Equation (9-5)].

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Note the similarity between this equation and Equations (7-57) and (7-58).

Box 9-B

Genetic Disorders: Refsum's Disease

This inherited (autosomal recessive) Lipid METABOLISM disorder leads to the accumulation of phytanic acid, a 20-carbon branched-chain fatty acid, in Tissues. Phytanic acid is normally produced in the body from phytol, a plant alcohol that is esterified as part of chlorophyll (Fig. 13-19). Since the β-oxidation of phytanic acid is blocked, its breakdown begins with α-oxidation, followed by β-oxidation to yield (from a single starting molecule) three molecules of propionyl-CoA, three molecules of acetyl-CoA, and one molecule of isobutyryl-CoA.

Patients with Refsum's disease are unable to oxidize phytanic acid due to impairments in the α-oxidation systema. It remains difficult to determine definitively whether the severe neurological disorders observed in Refsum's disease are caused by the accumulation of phytanic acid in Brain tissue or by the failure of the brain to synthesize certain essential odd-chain Fatty acids.

Question for the reader: What is the most likely effect of incorporating phytanic acid into brain Cell membranes?

а Steinberg D., Herndon J. Н., Jr., Uhlendorf В. W., Mize C. F., Avigan Milne G. W. A., Science, 156, 1740—1742 (1967).



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