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.
In this study, we isolated caffeine synthase orthologous genes from 12 species of Theaceae. Three recombinant enzymes which were approximately 70% homologous to tea caffeine synthase did not show theobromine synthase activity. The molecular evolutions of these methyltransferases were discussed.
