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1: Science. 1997 Jan 17;275(5298):362-6.Click here to read Links
Comment in:
Science. 1997 Jan 17;275(5298):306.

Stereoselective bimolecular phenoxy radical coupling by an auxiliary (dirigent) protein without an active center.

Davin LB, Wang HB, Crowell AL, Bedgar DL, Martin DM, Sarkanen S, Lewis NG.

Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.

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 presence of an oxidase or one electron oxidant, effects stereoselective bimolecular phenoxy radical coupling in vitro. Itself lacking a catalytically active (oxidative) center, its mechanism of action is presumed to involve capture of E-coniferyl alcohol-derived free-radical intermediates, with consequent stereoselective coupling to give (+)-pinoresinol.

PMID: 8994027 [PubMed - indexed for MEDLINE]

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