Ishida Mariko, Kitao Naoko, Mizuno Kouichi, Tanikawa Natsu, Kato Misako
Graduate School of Humanities and Sciences, Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo, 112-8610, Japan.
Planta. 2009 Feb;229(3):559-68. doi: 10.1007/s00425-008-0847-5. Epub 2008 Nov 19.
Caffeine (1,3,7-trimethylxanthine) and theobromine (3,7-dimethylxanthine) are purine alkaloids that are present in high concentrations in plants of some species of Camellia. However, most members of the genus Camellia contain no purine alkaloids. Tracer experiments using [8-(14)C]adenine and [8-(14)C]theobromine showed that the purine alkaloid pathway is not fully functional in leaves of purine alkaloid-free species. In five species of purine alkaloid-free Camellia plants, sufficient evidence was obtained to show the occurrence of genes that are homologous to caffeine synthase. Recombinant enzymes derived from purine alkaloid-free species showed only theobromine synthase activity. Unlike the caffeine synthase gene, these genes were expressed more strongly in mature tissue than in young tissue.
咖啡因（1,3,7 - 三甲基黄嘌呤）和可可碱（3,7 - 二甲基黄嘌呤）是嘌呤生物碱，在某些山茶属植物中含量很高。然而，山茶属的大多数成员不含嘌呤生物碱。使用[8 - (14)C]腺嘌呤和[8 - (14)C]可可碱的示踪实验表明，在不含嘌呤生物碱的物种的叶片中，嘌呤生物碱途径并不完全起作用。在五种不含嘌呤生物碱的山茶属植物中，获得了充分的证据表明存在与咖啡因合酶同源的基因。源自不含嘌呤生物碱物种的重组酶仅表现出可可碱合酶活性。与咖啡因合酶基因不同，这些基因在成熟组织中的表达比在幼嫩组织中更强。
