Stereoselective Bimolecular Phenoxy Radical Coupling by an Auxiliary (Dirigent) Protein Without an Active Center

@article{Davin1997StereoselectiveBP,
  title={Stereoselective Bimolecular Phenoxy Radical Coupling by an Auxiliary (Dirigent) Protein Without an Active Center},
  author={Laurence B. Davin and Huaiqiu Wang and Anastasia L. Crowell and Diana L. Bedgar and Diane M. Martin and Simo Sarkanen and Norman G. Lewis},
  journal={Science},
  year={1997},
  volume={275},
  pages={362 - 367}
}
The regio- and stereospecificity of bimolecular phenoxy radical coupling reactions, of especial importance in lignin and lignan biosynthesis, are clearly controlled in some manner in vivo; yet in vitro coupling by oxidases, such as laccases, only produce racemic products. In other words, laccases, peroxidases, and comparable oxidases are unable to control regio- or stereospecificity by themselves and thus some other agent must exist. A 78-kilodalton protein has been isolated that, in the… 
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TLDR
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TLDR
Feeding experiments proved that it is not the coumarin siderin but its hydroxy derivative, demethylsiderin, that undergoes phenol coupling, and the absence of other monomeric or dimeric coumarins strongly suggests an intermolecular, regio‐ and stereoselective mode for the phenol‐coupling step.
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