Nicotianamine is a metal-chelating molecule ubiquitous in higher plants. Biochemically, it is synthesized by the enzyme nicotianamine synthase, which uses three molecules of S-adenosylmethionine. Nicotianamine is a metal-chelating molecule ubiquitous in higher plants. Biochemically, it is synthesized by the enzyme nicotianamine synthase, which uses three molecules of S-adenosylmethionine.