title: Identification of a flavin-monooxygenase as the S-oxygenating enzyme in aliphatic glucosinolate biosynthesis in Arabidopsis.
abstract: 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, FMO(GS-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 FMO(GS-OX1) overexpression lines and an FMO(GS-OX1) knock-out mutant of Arabidopsis. The FMO(GS-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 FMO(GS-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.
authors.affiliation: Plant Biochemistry Laboratory, Department of Plant Biology, Faculty of Life Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark.
authors.forename: Bjarne G
authors.initials: BG
authors.lastname: Hansen
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Kliebenstein
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Halkier
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001937:Brassica / Q000201:enzymology / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D005415:Flavins / Q000378:metabolism*; D017353:Gene Deletion; D005961:Glucosinolates / Q000096:biosynthesis*; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D012275:Oryza / Q000201:enzymology / Q000235:genetics; D010940:Plant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D005415:Flavins; D005961:Glucosinolates; D010940:Plant Proteins; D006899:Mixed Function Oxygenases