Physics Colloquium - Friday, March 24th, 2006, 4:00 P.M.

E300 Math/Science Center; Refreshments at 3:30 P.M. in Room E200

Carsten Krebs
Pennsylvania State University

Oxygen Activation by the alpha-Ketoglutarate-Dependent Dioxygenases

The Fe(II) and a-ketoglutarate-dependent dioxygenases couple the activation of dioxygen at a mononuclear non-heme Fe-center to the hydroxylation of their substrates and the decarboxylation of a-ketoglutarate. These enzymes catalyze many biologically important reactions, such as sensing of oxygen in eukaryotes, repair of DNA, processes relevant to gene regulation, and biosynthesis of antibiotics. By using a combination of kinetic (stopped-flow and freeze-quench) and spectroscopic (UV/vis, Mossbauer, EPR, X-ray absorption) methods, we identified and characterized two reaction intermediates in the oxygen activation reaction of one member of this enzyme family, taurine:a-ketoglutarate dioxygenase, and thus, provided insights into the molecular mechanism of this enzyme. More recently, we studied the oxygen activation reaction of another a-ketoglutarate-dependent enzyme, prolyl-4-hydroxylase, and demonstrated the same two reaction intermediates in this reaction. These results provide the first experimental evidence for the long-held assumption that the a-ketoglutarate-dependent dioxygenases operate by a consensus mechanism.