Abstract
Recent investigations on caffeine biosynthesis pathways in leaves of Coffea arabica and Camellia sinensis, using both in vitro and in vivo test systems, are reviewed with special interest being focused on the proposal that the N-7 methyl acceptor is xanthosine monophosphate rather than xanthosine. In addition, studies on the isolation on the N-methyltransferases involved in caffeine biosynthesis which have succeeded in separating N-7 methyltransferase activity from the N-1- and N-3 methyltransferase activities are discussed. Purine alkaloid catabolism pathways are also discussed in the light of recent evidence demonstrating salvage of 3-methylxanthine and xanthine for the resynthesis of not only theophylline but also caffeine via theobromine. These pathways operate in leaves of tea but not those of coffee.