Catalyzes the conversion of methylthioalkyl glucosinolates of any chain length into methylsulfinylalkyl glucosinolates. a (Z)-omega-(methylsulfanyl)-N-sulfo-alkylhydroximate S-glucoside + H(+) + NADPH + O2 = a (Z)-omega-(methylsulfinyl)-alkyl-glucosinolate + H2O + NADP(+) Increased accumulation of methylthiobutyl, -pentyl, -heptyl and -octyl glucosinolates in leaves and seeds. Belongs to the FMO family.