Fig. 1 in Molecular and biochemical characterization of Catharanthus roseus perivine-N -methyltransferase

Fig. 1. The assembly of monoterpenoid indole alkaloids in different plant species involve substrate specific N-methylations catalysed by members of a recently described tocopherol-like methyltransferase gene family. The formation of strictosidine from secologanin and tryptamine involves the enzyme, strictosidine synthase (STR), while strictosidine-β-glucosidase (SGD) generates reactive intermediates, including 4, 21-dhydrogeissoschizine that is converted to 19Egeissoschizine by geissoschizine synthases (GS). This MIA is converted via multiple known enzyme reactions to 16-methoxy-2,3-dihydro-3-hydroxytabersonine which is N-methylated via dihydrotabersonine-N-methyltransferase (DhtNMT) to form 16-methoxy-2,3-dihydro-3-hydroxy-N-methyltabersonine that is ultimately converted into vindoline. While the conversion of 19E-geissoschizine to picrinine remains to be established, both Rauvolfia serpentina and Vinca minor express picrinine- N-methyltransferases (PiNMT) that converts picrinine to N-methypicrinine (ervincine). The formation of polyneuridine aldehyde from 19E-geissoschizine involves sarpagan bridge enzyme (SBE). Additional enzymes [polyneuridine aldehyde esterase (PNAE), vinorine synthase (VS), vinorine hydrolase, vinorine reductase and acetyajmaline esterase (AAE) convert vinorine to norajmaline. Two separate tocopherol-like methyltransferases (norajmaline N-methyltransferase (NNMT) and ajmaline N-methyltransferase convert norajmaline to ajmaline and Nβ-ajmaline, respectively. C. roseus and related species accumulate periformylene, an oxidixed form of Nβ-methylperivine. This MIA is derived from uncharacterized biochemical conversions of polyneuridine aldehyde to pericyclivine and to perivine. The formation of vobasine from perivine involves CrPeNMT found in C. roseus.