@article{HartmannSchrapersUteschetal.2016,
  author    = {Hartmann, Tobias and Schrapers, Peer and Utesch, Tillmann and Nimtz, Manfred and Rippers, Yvonne and Dau, Holger and Mroginski, Maria Andrea and Haumann, Michael and Leimk{\"u}hler, Silke},
  title     = {The Molybdenum Active Site of Formate Dehydrogenase Is Capable of Catalyzing C-H Bond Cleavage and Oxygen Atom Transfer Reactions},
  series = {Biochemistry},
  volume    = {55},
  journal   = {Biochemistry},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0006-2960},
  doi       = {10.1021/acs.biochem.6b00002},
  pages     = {2381 -- 2389},
  year      = {2016},
  abstract  = {Formate dehydrogenases (FDHs) are capable of performing the reversible oxidation of formate and are enzymes of great interest for fuel cell applications and for the production of reduced carbon compounds as energy sources from CO2. Metal containing FDHs in general contain a highly conserved active site, comprising a molybdenum (or tungsten) center coordinated by two molybdopterin guanine dinucleotide molecules, a sulfido and a (seleno-)cysteine ligand, in addition to a histidine and arginine residue in the second coordination sphere. So far, the role of these amino acids in catalysis has not been studied in detail, because of the lack of suitable expression systems and the lability or oxygen sensitivity of the enzymes. Here, the roles of these active site residues is revealed using the Mo-containing FDH from Rhodobacter capsulatus. Our results show that the cysteine ligand at the Mo ion is displaced by the formate substrate during the reaction, the arginine has a direct role in substrate binding and stabilization, and the histidine elevates the pK(a) of the active site cysteine. We further found that in addition to reversible formate oxidation, the enzyme is further capable of reducing nitrate to nitrite. We propose a mechanistic scheme that combines both functionalities and provides important insights into the distinct mechanisms of C-H bond cleavage and oxygen atom transfer catalyzed by formate dehydrogenase.},
  language  = {en}
}
@article{CorreiaOtreloCardosoSchwuchowetal.2016,
  author    = {Correia, Marcia A. S. and Otrelo-Cardoso, Ana Rita and Schwuchow, Viola and Clauss, Kajsa G. V. Sigfridsson and Haumann, Michael and Romao, Maria Joao and Leimk{\"u}hler, Silke and Santos-Silva, Teresa},
  title     = {The Escherichia coli Periplasmic Aldehyde Oxidoreductase Is an Exceptional Member of the Xanthine Oxidase Family of Molybdoenzymes},
  series = {ACS chemical biology},
  volume    = {11},
  journal   = {ACS chemical biology},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1554-8929},
  doi       = {10.1021/acschembio.6b00572},
  pages     = {2923 -- 2935},
  year      = {2016},
  abstract  = {The xanthine oxidase (XO) family comprises molybdenum-dependent enzymes that usually form homodimers (or dimers of heterodimers/trimers) organized in three domains that harbor two [2Fe-2S] clusters, one FAD, and a Mo cofactor. In this work, we crystallized an unusual member of the family, the periplasmic aldehyde oxidoreductase PaoABC from Escherichia coli. This is the first example of an E. coli protein containing a molybdopterin-cytosine-dinucleotide cofactor and is the only heterotrimer of the XO family so far structurally characterized. The crystal structure revealed the presence of an unexpected [4Fe-4S] cluster, anchored to an additional 40 residues subdomain. According to phylogenetic analysis, proteins containing this cluster are widely spread in many bacteria phyla, putatively through repeated gene transfer events. The active site of PaoABC is highly exposed to the surface with no aromatic residues and an arginine (PaoC-R440) making a direct interaction with PaoC-E692, which acts as a base catalyst. In order to understand the importance of R440, kinetic assays were carried out, and the crystal structure of the PaoC-R440H variant was also determined.},
  language  = {en}
}