Chloroperoxidase compound I: electron paramagnetic resonance and Moessbauer studies

摘要: The green primary compound of chloroperoxidase was prepared by freeze-quenching the enzyme after rapid mixing with a 5-fold excess peracetic acid. electron paramagnetic resonance (EPR) spectra these preparations consisted at least three distinct signals that could be assigned to native enzyme, free radical, and I as reported earlier. absorption spectrum obtained through subtraction EPR measured under passage conditions. signal is well approximated an effective spin Seff = 1/2 model g 1.64, 1.73, 2.00 highly anisotropic line width. Mossbauer difference samples minus showed well-resolved magnetic splitting 4.2 K, isomer shift delta Fe 0.15 mm/s, quadrupole EQ 1.02 mm/s. All data are consistent exchange-coupled S 1 ferryl iron S' porphyrin radical. As result large zero field splitting, D, intermediate antiferromagnetic exchange, S.J.S'.J approximately system consists Kramers doublets widely separated in energy. relates ground doublet intrinsic parameters iron, D/k 52 E/D congruent 0.035, A perpendicular (gn beta n) 20 T, radical.(ABSTRACT TRUNCATED AT 250 WORDS)