Abstract
Caffeine and theobromine are purine alkaloids that are present in high concentrations in plants of some species of Camellia. The main caffeine biosynthetic pathway involves in three S-Adenosyl-L-methionine (SAM)-dependent methylation steps. SAM-dependent N-methyltransferases play an important role in the regulation of caffeine biosynthesis. Caffeine synthase catalyzes 1-N and 3-N-methylation reaction of mono- or di-methylxanthines, on the other hand, theobromine synthase catalyzes 3-N-methylation reaction of 7-methylxanthine. Recently we reported occurrence of theobromine synthase genes in purine alkaloid-free species of Camellia plants. Caffeine synthase and theobromine synthase are members of motif B' methyltransferase family which have motif B' and YFFF region.
In this study, we isolated 20 motif B' methyltransferase genes from 12 species of Theaceae. Recombinant enzymes from Gordonia acuminata and Eurya japonica showed theobromine synthase activity and salicylic acid carboxylmethyltransferase activity, respectively. The molecular evolution of these methyltransferases were discussed.
