The reducing component BoxA of benzoyl-coenzyme A epoxidase from Azoarcus evansii is a [4Fe-4S] protein.

Liv J Rather, Eckhard Bill, Wael Ismail, Georg Fuchs, Liv J Rather, Eckhard Bill, Wael Ismail, Georg Fuchs, Liv J. Rather, Eckhard Bill, Wael Ismail, Georg Fuchs

Index: Biochim. Biophys. Acta 1814(12) , 1609-1615, (2011)

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Abstract

BoxA is the reductase component of the benzoyl-coenzyme A (CoA) oxidizing epoxidase enzyme system BoxAB. The enzyme catalyzes the key step of an hitherto unknown aerobic, CoA-dependent pathway of benzoate metabolism, which is the epoxidation of benzoyl-CoA to the non-aromatic 2,3-epoxybenzoyl-CoA. The function of BoxA is the transfer of two electrons from NADPH to the epoxidase component BoxB. We could show recently that BoxB is a diiron enzyme, whereas here we demonstrate that BoxA harbors an FAD and two [4Fe-4S] clusters per protein monomer. The characterization of BoxA was hampered by severe oxygen sensitivity; the cubane [4Fe-4S] clusters degrade already with traces of oxygen. Interestingly, the adventitiously formed [3Fe-4S] centers could be reconstituted in vitro by adding Fe(II) and sulfide to retrieve the native cubane centers. BoxA is the first example of a reductase of this type that has an FAD and two bacterial ferredoxin-type [4Fe-4S] clusters. In other cases within the catalytically versatile family of diiron enzymes, the related reductases have plant-type ferredoxin or Rieske-type [2Fe-2S] centers only.Copyright © 2011 Elsevier B.V. All rights reserved.