Flavin-monooxygenase (FMO) enzyme; FMOGS-OX1 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 (Hansen et al. 2007)