常绿茶树的嘌呤代谢与其他多数有机体不同,因为它具有一从嘌呤核苷酸到咖啡碱的特殊代谢途径。尽管在花等器官中观察到咖啡碱,其生物合成主要在叶片中。茶叶咖啡碱含量的季节变化已有报道,茶叶的嘌呤代谢在年周期中似乎有相当大的波动。本研究检测了茶叶嘌呤代谢的季节性变化,并测定了咖啡碱生物合成中几个关键酶的活性。结果表明:咖啡碱在早期发育阶段(4～6月)的茶丛叶片中,由腺嘌呤核苷酸合成,合成速率看来主要取决于N-甲基转 Purine metabolism of the evergreen tea tree differs from most other organisms in that it has a specific metabolic pathway from purine nucleotides to caffeine. Although caffeine is observed in flowers and other organs, its biosynthesis is mainly in the leaves. Seasonal changes in the caffeine content of tea have been reported, and purine metabolism in tea appears to fluctuate considerably in the annual cycle. This study examined the seasonal changes of purine metabolism in tea and determined the activities of several key enzymes in caffeine biosynthesis. The results showed that caffeine was synthesized from adenine nucleotides in tea leaves at early developmental stages (April-June), and the rate of synthesis seems to depend primarily on N-methyl