Redox chemistry of biological tungsten: an EPR study of the aldehyde oxidoreductase from Pyrococcus furiosus |
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Authors: | Alexander F Arendsen Marcel de Vocht Yvonne B M Bulsink W R Hagen |
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Institution: | (1) Department of Biochemistry, Wageningen Agricultural University, Dreijenlaan 3, 6703 HA Wageningen,, |
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Abstract: | Aldehyde:ferredoxin oxidoreductase (AOR) from the hyperthermophilic archaeon Pyrococcus furiosus is a homodimeric protein. Each subunit carries one 4Fe-4S] cubane and a novel tungsten cofactor containing two pterins.
A single iron atom bridges between the subunits. AOR has previously been studied with EPR spectroscopy in an inactive form
known as the red tungsten protein (RTP): reduced RTP exhibits complex EPR interaction signals. We have now investigated the
active enzyme AOR with EPR, and we have found an S = 1/2 plus S = 3/2 spin mixture from a non-interacting 4Fe-4S]1+ cluster in the reduced enzyme. Oxidized AOR affords EPR signals typical for W(V) with g–values of 1.982, 1.953, and 1.885. The W(V) signals disappear at a reduction potential E
m,7.5 of +180 mV. This unexpectedly high value indicates that the active-site redox chemistry is based on the pterin part of the
cofactor.
Received: 18 December 1995 / Accepted: 26 March 1996 |
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Keywords: | Aldehyde:ferredoxin oxidoreductase Iron-sulfur cluster Tungsten EPR Pyrococcus furiosus |
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