The studied aldehyde oxidoreductase enzyme (AOR) incorporates in its active center a tungsten ion, the heaviest element with biological function. Tungsten-containing enzymes occur only in bacteria and archaea, are very oxygen-sensitive and catalyze reactions with very low redox potential.
The studied AOR was isolated from Aromatoleum aromaticum (AORAa) a mesophilic and facultative anaerobic bacterium. AORAa characteristics differ significantly from the best-studied examples of AOR from the hyperthermophilic archaea. It is less oxygen-sensitive and has a more complicated structure. The AORAa catalyzes the oxidation of a broad variety of aldehydes to the respective acids with either viologen dyes or NAD+ as electron acceptors.
Fig 1. AOR catalyzes O2-independent oxidation of aldehydes to corresponding carboxylic acids or the reverse reaction in a two-electron redox reaction.
Our research aims to characterize the structure of the protein and its catalytic properties as well as solve
the mechanism of the catalyzed reaction. To achieve that we combine the experimental methods ( i.e. kinetic measurements) with theoretical approaches.
Fig.2. Hypothetical model of AOR from Aromatoleum aromaticum complex: blue-catalytic subunit containing the tungsten cofactor (Wco) as a catalytic center and one Fe4S4 cluster, greeb-the electron transfer subunit containing four Fe4S4 clusters, red-subunit containing a FAD cofactor.
The project is conducted under the NCN grant PRELUDIUM No 2017/27/N/ST4/02676: ‘Tungsten-containing aldehyde oxidoreductase from Aromatoleum aromaticum - a study of catalytic reaction mechanism’
List of papers:
 Arndt F, Schmitt G, Winiarska A, Saft M, Seubert A, Kahnt J and Heider J (2019) Characterization of an Aldehyde Oxidoreductase From the Mesophilic Bacterium Aromatoleum aromaticum EbN1, a Member of a New Subfamily of Tungsten-Containing Enzymes. Front. Microbiol. 10:71. doi: 10.3389/fmicb.2019.00071