This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Refsum's disease is due to deficiency of which of the following enzyme? 
Select and explain. 
A. Malonate dehydrogenase, B. Thiophorase, C. Succinate thiokinase, D. Phytanic alpha oxidase
D: Phytanic alpha oxidase
Answer: D: Phytanic alpha oxidase 
Explanation: Phytanic alpha oxidase 

Refsum disease is caused by a deficiency of phytanic acid α -hydroxylase (α -oxidase) which is required for a-oxidation of methylated fatty acids, phytanic acid.