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![Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F55858.jpg&w=3840&q=50)
Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase
Published on: December 4, 2017
The Keto Functions of Heme d1 Are Introduced by NirF and NirC
1Institut für Pharmazeutische Wissenschaften, Pharmazeutische Biologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
Abstract:
The modified tetrapyrrole heme d1 plays an important role for bacterial denitrification as essential cofactor of the cytochrome cd1 nitrite reductase. Structurally, heme d1 is a dioxo-isobacteriochlorin carrying two keto functions on pyrrole rings A and B. While most of the steps of heme d1 biosynthesis were elucidated, the introduction of the keto functions remained enigmatic. In this study, we show that the proteins NirF and NirC catalyze the formation of the keto functions. NirF binds the nonenzymatically formed dilactone form of 3,8-dideoxo-dihydro-heme d1 and together with NirC transforms this intermediate into dihydro-heme d1 as shown by HPLC-UV/Vis and HPLC-MS analysis. The additional oxygen atoms of dihydro-heme d1 derive from water based on experiments performed with 18O-labeled H2O.
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