Peroxisomal phytanoyl-CoA dioxygenase catalyzes the reaction of phytanoyl-CoA, 2-oxoglutarate, and O2 to form 2-hydroxyphytanoyl-CoA, succinate, and CO2. The mature form of the enzyme lacks the first 30 amino acid residues of the full-length polypeptide and is complexed with Fe++. Mutations in this enzyme are the commonest cause of Refsum disease (Mukherji et al. 2001; McDonough et al. 2005).