Figure 8.

Alkaloid classes that require 2-oxoglutarate as a co-substrate. These N-heterocyclic molecules are often synthesized in preparation for growth of new tissue and serve as an on-demand nitrogen source accessible at all times. As the tissues grow and differentiate, alkaloid reserves have been shown to progressively deplete. (A) (S)-norcoclaurine is the precursor of the isoquinoline classs of alkaloids (codeine, thebaine). These require demethylases, which interconvert them. (B) The vinca alkaloids (precursor: deacetoxyvindoline), are inhibitors of microtubule transport and terminally synthesized compounds (vincristine, vinblastine) are used in various chemotherapy regimens. (C) The tropanes are best represented by hyoscyamine and scopolamine both of which require activity of H6H (Hyoscyamine 6β-hydoxylase).