Abstract
The caffeine(1,3,7-trimethylxanthine) biosynthetic pathway contains three S-adenosylmethionine(SAM)-dependent methylation steps. Caffeine synthase(CS), which is investigated by our group, is the SAM-dependent N-methyltransferase. CS is involved in the last two steps(N-1 and N-3 methylation) of caffeine biosynthesis in tea leaves.
In this study, we isolated tea caffeine synthase(TCS) homologous gene BTS1 from cacao(Theobroma cacao) leaves that accumulate theobromine(3,7-dimethylxanthine) as the predominant purine alkaloid by RACE. The estimated molecular mass of BTS1 was 41 kDa and it was similar to that of TCS and CTS which was theobromine synthase from coffee. The identity of amino acid sequence between BTS1 and TCS1, BTS1 and CTS1 were 55 and 35%, respectively. Recombinant BTS1 catalyzed the conversion of 7-methylxanthine to theobromine, suggesting that BTS1 was theobromine synthase.
