trans-aconitate + S-adenosyl-L-methionine => (E)-3-(methoxycarbonyl)pent-2-enedioate + S-adenosyl-L-homocysteine
trans-aconitate + s-adenosyl-l-methionine => (e)-3-(methoxycarbonyl)pent-2-enedioate + s-adenosyl-l-homocysteine