title: Pulse radiolysis study of a yeast cytochrome c from Hansenula anomala.
abstract: The reduction of Hansenula anomala yeast cytochrome c by e-aq and CO-.2 was investigated by pulse radiolysis, at a high reductant to protein concentration ratio. The reactivity of the radicals was studied by observing absorbance changes in the cytochrome c spectrum over the wavelength range 280-600 nm. At pH 7, over the time scale of the radical decays (i.e. 0-4 microseconds for e-aq; 0-40 microseconds for CO-.2s) and beyond, the hemoprotein was reduced without any spectrally detected intermediate between ferri-and ferro-forms. This conclusion was reached by simulation studies based on the direct reduction of the yeast cytochrome c from the ferri- to the ferro-form, yielding a correct fit between experimental and calculated absorbance curves. The reduction rate constants were determined to be 1.0 +/- 01 X 10(10) M-1 S-1 for e-aq and 0.7 +/- 0.05 X 10(9) M-1 S-1 for CO-.2 at 0.16 M ionic strength, pH 7.0 and 20 degrees C, thus not significantly different from other values reported for horse heart cytochrome c. However, in the 360-390 nm region the generation of an additional radical species was noticed. The present experimental data were compared with previously published reports.
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism*; D004583:Electrons; D005609:Free Radicals; D007700:Kinetics; D010084:Oxidation-Reduction; D010843:Pichia / Q000032:analysis*; D011675:Pulse Radiolysis; D004718:Saccharomycetales / Q000032:analysis*; D012996:Solutions; D013053:Spectrophotometry; D014867:Water
chemical_list: D003574:Cytochrome c Group; D005609:Free Radicals; D012996:Solutions; D014867:Water; D002245:Carbon Dioxide; C041069:carboxyl radical