ENZYMOLOGY OF INDOLE ALKALOID BIOSYNTHESIS IN CATHARANTHUS-ROSEUS

Indole alkaloids in Catharanthus roseus have been in focus because of their medicinal value. These alkaloids consist of an indole moiety pro vided by tryptamine and a terpenoid portion provided by the secologani n. The most important catharanthus alkaloids are vinblastine (VLB), vi ncristine (VCR) and ajmalicine. VLB and VCR are clinically useful anti cancer agents whereas ajmalicine is used for the treatment of circulat ory diseases. VCR and VLB are the most expensive because of their low abundance in the plant, and are formed by the coupling of monomeric in dole alkaloids vindoline and catharanthine, catalysed by peroxidases. The pathway that lead to monomeric indole alkaloids involves more than 20 enzymes of which 16 enzymes have been isolated and characterized b iochemically, and only three at the, molecular level. The present stat e of knowledge on enzymes and genes involved in indole alkaloid biosyn thesis and various aspects of their regulation has been discussed.