XVI International Botanical Congess

Caffeine synthase (CS), the SAM-dependent N-methyltransferase involved in the last two steps of the caffeine biosynthesis, was extracted from young tea leaves (Camellia sinensis) and was purified 520-fold to apparent homogeneity by ammonium sulphate fractionation, hydroxyapatite, anion-exchange, adenosine-agarose and gel-filtration. The enzyme was monomeric with an apparent molecular mass of 61kD as estimated by gel-filtration and 41 kD when analysed by SDS-PAGE. The final preparation exhibited 3- and 1-N-methyltransferase activity with a broad substrate specificity, showing high activity toward paraxanthine, 7-methylxanthine and theobromine. However, the enzyme has no 7-N-methyltransferase activity toward xanthosine and XMP.