Enzymatic ω-Oxidation

Rubredoxin, a red, nonheme iron protein previously shown to function as an electron carrier in the ω-hydroxylation of fatty acids and hydrocarbons in enzyme preparations from Pseudomonas oleovorans, has been obtained in highly purified form. The apparent molecular weight is 12,800. Two atoms of iron are present per molecule, but no labile sulfide. In the oxidized form this protein exhibits absorption maxima at 495, 377, and 280 mµ, with a molar extinction coefficient at 495 mµ of 1.11 x 104. Oxidized rubredoxin gives electron paramagnetic resonance signals at g = 4.3 and 9.4, which is characteristic of high spin ferric ion in a rhombic field. A quantitative comparison of the loss of absorbance at 495 mµ and of electron paramagnetic resonance at g = 4.3 upon the reduction of rubredoxin by TPNH, in the presence of spinach TPNH-ferredoxin reductase, indicated that 1 electron is accepted per atom of iron. The reduction potential is -0.037 volt. Rubredoxin gives intense and detailed optical rotatory dispersion and circular dichroism spectra which indicate that the iron-ligand chromophores are in a highly asymmetric environment.