CD and MCD Studies of the Non-Heme Ferrous Active Site in (4-Hydroxyphenyl)pyruvate Dioxygenase: Correlation between Oxygen Activation in the Extradiol and α-KG-Dependent Dioxygenases

(4-Hydroxyphenyl)pyruvate dioxygenase (HPPD) is an unusual alpha-keto acid-dependent non-heme iron dioxygenase as it incorporates both atoms of dioxygen into a single substrate, paralleling the extradiol dioxygenases. CD/MCD studies of the catalytically active ferrous site and its interaction with substrate reveal a geometic and electronic structure and mechanistic approach to oxygen activation which bridges those of the alpha-KG-dependent and the extradiol dioxygenases.