Strictosidine: from alkaloid to enzyme to gene.

In this review, the elucidation of the structure of the first key alkaloidal intermediate in monoterpenoid indole alkaloid biosynthesis, 3 alpha(S)-strictosidine, is presented. The discovery of the enzyme which catalyses the stereospecific formation of this alkaloidal precursor from tryptamine and secologanin, strictosidine synthase, is also detailed. From the knowledge provided by the stereochemical structure of strictosidine and the biochemical characteristics of the biosynthetic enzyme, strictosidine synthase, a new approach to the study of monoterpenoid indole alkaloid biosynthesis was developed. Physiological studies of monoterpenoid indole alkaloid biosynthesis at the enzymic level in plants and plant cell cultures were performed followed by the analyses of these systems at the level of molecular genetics.