Caffeine synthase

Caffeine synthase is a methyltransferase enzyme involved in the caffeine biosynthesis pathway. It is expressed in tea species, coffee species, and cocoa species. The enzyme catalyses the following reactions:

S-adenosyl-L-methionine + theobromine S-adenosyl-L-homocysteine + caffeine + H⁺S-adenosyl-L-methionine + paraxanthine S-adenosyl-L-homocysteine + caffeine + H⁺
7-methylxanthine + S-adenosyl-L-methionine S-adenosyl-L-homocysteine + H⁺ + theobromine

Caffeine synthase is expressed in the Camellia species irrawadiensis, ptilophylla, and sinensis; the Coffea species arabica, and canephora; and in Theobroma cacao.