By heterologous expression in Escherichia and the correlation of gene expression patterns to the GSL phenotype. AOP2 catalyzes the conversion of methylsulfinylalkyl GSLs to alkenyl GSLs in Arabidopsis. Absence of functional AOP2 and AOP3 leads to the accumulation of the precursor methylsulfinylalkyl GSLs (Kliebenstein et al. 2001)