In enzymology, a phytanoyl-CoA dioxygenase (EC 1.14.11.18) is an enzyme that catalyzes the chemical reaction

The mechanism is complex, but is believed to involve ordered binding of 2-oxoglutarate to the iron(II) containing enzyme followed by substrate.

[4] In humans, phytanoyl-CoA hydroxylase is encoded by the PHYH (aka PAHX) gene and is required for the alpha-oxidation of branched chain fatty acids (e.g. phytanic acid) in peroxisomes.

PHYH deficiency results in the accumulation of large tissue stores of phytanic acid and is the major cause of Refsum disease.

[2] In plants and microorganisms this enzyme family is associated with a large diversity of oxidative reactions.