Rauvolfia serpentina N-methyltransferases involved in ajmaline and Nβ -methylajmaline biosynthesis belong to a gene family derived from γ-tocopherol C-methyltransferase.
Ajmaline biosynthesis in Rauvolfia serpentina has been one of the most studied monoterpenoid indole alkaloid (MIA) pathways within the plant family Apocynaceae. Detailed molecular and biochemical information on most of the steps involved in the pathway has been generated over the last 30 years. Here we report the identification, molecular cloning and functional expression in Escherichia coli of two R. serpentinacDNAs that are part of a recently discovered γ-tocopherol-like N-methyltransferase (γ-TLMT) family and are involved in indole and side-chain N-methylation of ajmaline. Recombinant proteins showed remarkable substrate specificity for molecules with an ajmalan-type backbone and strict regiospecific N-methylation. Furthermore, N-methyltransferase gene transcripts and enzyme activity were enriched in R. serpentina roots which correlated with accumulation of ajmaline alkaloid. This study elucidates the final step in the ajmaline biosynthetic pathway and describes the enzyme responsible for the formation of Nβ -methylajmaline, an unusual charged MIA found in R. serpentina.
Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock Way, St Catharines, L2S 3A1, Canada.
Paulo
P
Cázares-Flores
Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock Way, St Catharines, L2S 3A1, Canada.
Dylan
D
Levac
Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock Way, St Catharines, L2S 3A1, Canada. vdeluca@brocku.ca.
Vincenzo
V
De Luca
D000404:Ajmaline / Q000096:biosynthesis* / Q000737:chemistry; D053898:Biosynthetic Pathways; D003001:Cloning, Molecular; D019295:Computational Biology; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000737:chemistry / Q000201:enzymology / Q000235:genetics; D011926:Rauwolfia / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins; D046948:Secologanin Tryptamine Alkaloids / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
D010940:Plant Proteins; D011994:Recombinant Proteins; D046948:Secologanin Tryptamine Alkaloids; D000404:Ajmaline; D008780:Methyltransferases; C047259:gamma-tocopherol methyltransferase
Apocynaceae; Rauvolfia serpentina; ajmaline Nβ-methyltransferase; monoterpenoid indole alkaloid; norajmaline N-methyltransferase; γ-tocopherol-like N-methyltransferase family