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A promiscuous cytochrome P450 aromatic O-demethylase for lignin bioconversion.

  • Author(s): Mallinson, Sam JB
  • Machovina, Melodie M
  • Silveira, Rodrigo L
  • Garcia-Borràs, Marc
  • Gallup, Nathan
  • Johnson, Christopher W
  • Allen, Mark D
  • Skaf, Munir S
  • Crowley, Michael F
  • Neidle, Ellen L
  • Houk, Kendall N
  • Beckham, Gregg T
  • DuBois, Jennifer L
  • McGeehan, John E
  • et al.
Abstract

Microbial aromatic catabolism offers a promising approach to convert lignin, a vast source of renewable carbon, into useful products. Aryl-O-demethylation is an essential biochemical reaction to ultimately catabolize coniferyl and sinapyl lignin-derived aromatic compounds, and is often a key bottleneck for both native and engineered bioconversion pathways. Here, we report the comprehensive characterization of a promiscuous P450 aryl-O-demethylase, consisting of a cytochrome P450 protein from the family CYP255A (GcoA) and a three-domain reductase (GcoB) that together represent a new two-component P450 class. Though originally described as converting guaiacol to catechol, we show that this system efficiently demethylates both guaiacol and an unexpectedly wide variety of lignin-relevant monomers. Structural, biochemical, and computational studies of this novel two-component system elucidate the mechanism of its broad substrate specificity, presenting it as a new tool for a critical step in biological lignin conversion.

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