Abstract
We present a complementary Mössbauer and EPR study on reaction intermediates of substrate-free and substrate-bound cytochrome P450cam from Pseudomonas putida prepared by the freeze-quench method from 57Fe-labeled P450cam using peroxy acetic acid as oxidizing agent. When reacting the substrate-free P450cam for 8 ms reaction time the reaction mixture consists of ∼85% of ferric low-spin iron (Fe(III)) with g-factors and hyperfine parameters of the starting material; the remaining ∼15% are identified as ferryl iron (Fe(IV); S Fe=1) by its Mössbauer signature. Parallel to the ferryl iron a tyrosine radical (S rad=1/2) is formed. The two paramagnetic species are not exchange-coupled; however, they are close enough to significantly influence the (EPR) relaxation behavior of the radical spin. In the case of substrate-bound P450cam only trace amounts of the tyrosine radical are formed within 8 ms (<3%); within the accuracy of Mössbauer spectroscopy (5%) iron(IV) can not be detected. The results point to Tyr-96, which is hydrogen-bonded to the substrate camphor, as the candidate for the observed tyrosine radical.
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Schünemann, V., Trautwein, A.X., Jung, C. et al. Mössbauer and EPR Study of Reaction Intermediates of Cytochrome P450. Hyperfine Interactions 141, 279–284 (2002). https://doi.org/10.1023/A:1021255431370
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DOI: https://doi.org/10.1023/A:1021255431370