Refsum disease is caused by phytanic acid oxidase (or phytanoyl-CoA synthetase) deficiency This enzyme is involved in the process of alpha-oxidation of fatty acids, which is required in order for phytanic acid to be converted into propionyl-CoA and used for energy. Phytanic acid is a branched-chain fatty acid (depicted below) that is a component of chlorophyll and is a significant component of milk. In people with Refsum disease, phytanic acid can accumulate, leading to neurological problems – vision loss, hearing loss, peripheral neuropathy, and neurodegeneration of the central nervous system. A. Why does phytanic acid accumulate without phytanic acid oxidase? Why can’t this compound be oxidized by beta-oxidation? Which step in beta-oxidation would be inhibited if phytanyl-CoA were produced in a normal individual? B. Compare alpha-oxidation to beta-oxidation using Figure 17-18 in your book. Why is phytanic acid a good candidate for alpha-oxidation? Why is propionyl-CoA rather than acetyl-CoA produced? C. What enzyme activity could you invent to prevent the accumulation of phytanic acid in Refsum disease patients?