title: Direct detection of oxygen intermediates in the non-heme Fe enzyme taurine/alpha-ketoglutarate dioxygenase.
abstract: The reaction of substrate-bound taurine/alpha-ketoglutarate dioxygenase with O2 has been studied using cryogenic continuous-flow spectroscopy. Transient absorption spectra acquired at -38 degrees C show an exponential decay of a 318-nm chromophore with an apparent rate of 1.3 s-1. The observed optical changes and their kinetics are consistent with the profile of an Fe(IV) species detected recently by Mössbauer spectroscopy (Price et al., Biochemistry 2003, 42, 7497-7508). Resonance Raman measurement upon excitation at 363.7 nm reveal at least two oxygen isotope-sensitive vibrations at 821/787 cm-1 and 583/555 cm-1 for 16O and 18O derivatives, respectively. An additional mode is likely to be obscured by an ethylene glycol vibration at 865 cm-1 and/or 1089 cm-1. The 821 cm-1 vibration is assigned to the stretching mode of Fe(IV)=O species on the basis of its frequency and isotopic shift amplitude. The 583 cm-1 band is likely to originate from an Fe-O2 precursor of the Fe(IV)=O species, although its structural details are unclear at present.
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA. denisp@cem.msu.edu
authors.forename: Denis A
authors.initials: DA
authors.lastname: Proshlyakov
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Henshaw
authors.forename: Greta R
authors.initials: GR
authors.lastname: Monterosso
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Ryle
authors.forename: Robert P
authors.initials: RP
authors.lastname: Hausinger
mesh_terms: D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000378:metabolism*; D019159:Nonheme Iron Proteins / Q000737:chemistry / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D010103:Oxygen Isotopes; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
chemical_list: D019159:Nonheme Iron Proteins; D010103:Oxygen Isotopes; D006899:Mixed Function Oxygenases; C433064:taurine-alpha-ketoglutarate dioxygenase; D010100:Oxygen