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Identification of a flavin‐monooxygenase as the S ‐oxygenating enzyme in aliphatic glucosinolate biosynthesis in Arabidopsis
Author(s) -
Hansen Bjarne G.,
Kliebenstein Daniel J.,
Halkier Barbara A.
Publication year - 2007
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2007.03101.x
Subject(s) - monooxygenase , enzyme , arabidopsis , flavin group , biochemistry , chemistry , glucosinolate , biosynthesis , identification (biology) , biology , gene , botany , cytochrome p450 , mutant , brassica
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, 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.