Aromatic dimer dehydrogenases from Novosphingobium aromaticivorans reduce aromatic diketones

Aromatic diketones are a major product of formic acid lignin depolymerization. Novosphingobium aromaticivorans can degrade these diketones, but the enzymes used in this process were unknown. We used RNA-Seq to identify aromatic dimer dehydrogenases as potential candidates for the initial reduction of the aromatic G-diketone, then verified this using in vitro enzyme assays. Comparison of G-type aromatic compounds (vanillic acid, vanillin, and ferulic acid), protocatechuic acid, G-diketone, and GP-1 (a reduced intermediate) to a glucose control. All conditions contain equimolar amounts of glucose and the selected aromatic substrates.