Identification of a flavin-monooxygenase as the S-oxygenating enzyme in aliphatic glucosinolate biosynthesis in Arabidopsis

Authors

  • Bjarne G. Hansen,

    1. Plant Biochemistry Laboratory, Department of Plant Biology, Faculty of Life Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark,
    Search for more papers by this author
  • Daniel J. Kliebenstein,

    1. University of California-Davis, Department of Plant Sciences, Mail Stop 3, One Shields Ave, Davis, CA 95616-8780, USA
    Search for more papers by this author
  • Barbara A. Halkier

    1. Plant Biochemistry Laboratory, Department of Plant Biology, Faculty of Life Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark,
    Search for more papers by this author

For correspondence (fax +0045 35283333; e-mail bah@LiFE.KU.DK).

Summary

The cancer-preventive activity of cruciferous vegetables is commonly attributed to isothiocyanates resulting from the breakdown of the natural products glucosinolates (GSLs). Sulforaphane, the isothiocyanate derived from 4-methylsulfinylbutyl GSL, is thought to be the major agent conferring cancer-preventive properties, whereas the isothiocyanate of 4-methylthiobutyl GSL does not have the same activity. We report the identification of an Arabidopsis flavin-monooxygenase (FMO) enzyme, FMOGS-OX1, which catalyzes the conversion of methylthioalkyl GSLs into methylsulfinylalkyl GSLs. This is evidenced by biochemical characterization of the recombinant protein, and analyses of the GSL content in FMOGS-OX1 overexpression lines and an FMOGS-OX1 knock-out mutant of Arabidopsis. The FMOGS-OX1 overexpression lines show almost complete conversion of methylthioalkyl into methylsulfinylalkyl GSLs, with an approximately fivefold increase in 4-methylsulfinylbutyl GSL in seeds. Identification of FMOGS-OX1 provides a molecular tool for breeding of Brassica vegetable crops with increased levels of this important GSL, which has implications for production of functional foods enriched with the cancer-preventive sulforaphane.

Ancillary