Catalyzes the conversion of methylthioalkyl glucosinolates of any chain length into methylsulfinylalkyl glucosinolates. Prefers probably short-chain methylthioalkyl glucosinolates in cv. Landsberg erecta. a (Z)-omega-(methylsulfanyl)-N-sulfo-alkylhydroximate S-glucoside + H(+) + NADPH + O2 = a (Z)-omega-(methylsulfinyl)-alkyl-glucosinolate + H2O + NADP(+) Down-regulated at late stage by auxin. Increased accumulation of methylthiopropyl glucosinolates in leaves and seeds. In contrast to cv. Columbia, cv. Landsberg erecta has predominantly propyl C3 instead of butyl C4 Met-derived glucosinolates. Belongs to the FMO family.