Metal Ion Promiscuity and Structure of 2,3‐Dihydroxybenzoic Acid Decarboxylase of <i>Aspergillus oryzae</i>
Gerhard Höfer, Xiang Sheng, Simone Braeuer, Stefan E. Payer, Katharina Plasch, Walter Goessler, Kurt Faber, Walter Keller, Fahmi Himo, Silvia M. Glueck
Abstract
Abstract Broad substrate tolerance and excellent regioselectivity, as well as independence from sensitive cofactors have established benzoic acid decarboxylases from microbial sources as efficient biocatalysts. Robustness under process conditions makes them particularly attractive for preparative‐scale applications. The divalent metal‐dependent enzymes are capable of catalyzing the reversible non‐oxidative (de)carboxylation of a variety of electron‐rich (hetero)aromatic substrates analogously to the chemical Kolbe‐Schmitt reaction. Elemental mass spectrometry supported by crystal structure elucidation and quantum chemical calculations verified the presence of a catalytically relevant Mg 2+ complexed in the active site of 2,3‐dihydroxybenoic acid decarboxylase from Aspergillus oryzae (2,3‐DHBD_ Ao ). This unique example with respect to the nature of the metal is in contrast to mechanistically related decarboxylases, which generally have Zn 2+ or Mn 2+ as the catalytically active metal.