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首页> 外文期刊>European Chemical Bulletin >CAFFEINE BIOSYNTHESIS AND PURINE METABOLISM IN LEAVES OF MASCAROCOFFEA SPECIES
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CAFFEINE BIOSYNTHESIS AND PURINE METABOLISM IN LEAVES OF MASCAROCOFFEA SPECIES

机译：牛油菌物种叶片中的咖啡因生物合成和嘌呤代谢

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摘要

Caffeine, a purine alkaloid, was not detected in leaves of two Mascarocoffea species, Coffea millotii and Coffea perrier. Trigonelline, a pyridine alkaloid, occurred in these species, but the levels (3?4 μmol/g fresh weight) were much lower than that of Robusta coffee (Coffea canephora) (36 μmol/g fresh weight). Feeding experiments with [8-14C]adenine indicated that purine alkaloid biosynthesis was terminated at 7-methylxanthine formation and as a consequence theobromine and caffeine were not produced in Coffea millotii and Coffea perrier. The adenine salvage activity was lower but its degradation activity was higher in leaves of these Mascarocoffea species than those in Coffea canephora. The metabolic fate of the purine nucleosides, [8-14C]inosine, [8-14C]guanosine and [8-14C]xanthosine was investigated in leaves of Coffea millotii. The biosynthesis of 7-methylxanthine, but not theobromine or caffeine, from these precursors was detected. Large amounts of these purine nucleosides were catabolized via allantoin. Limited amounts of [8-14C]inosine and [8-14C]guanosine were salvaged and utilized for RNA synthesis, however, no [8-14C]xanthosine salvage was observed. Little or no 14C-metabolites were observed when [8-14C]theobromine and [8-14C]caffeine were applied to leaf disks of Coffea millotii. From the results obtained in this study, possible metabolic pathways of purines in Mascarocoffea species are discussed.
机译：咖啡因是一种嘌呤生物碱，未在两种玛斯卡科弗尼亚种（咖啡因和咖啡因）的叶子中检出。这些物种中出现了Trigonelline，一种吡啶生物碱，但含量（3？4μmol/ g鲜重）远低于罗布斯塔咖啡（Coffea canephora）（36μmol/ g鲜重）。用[8-14C]腺嘌呤喂养的实验表明，嘌呤生物碱的生物合成终止于7-甲基黄嘌呤的形成，结果在咖啡因和咖啡因中未产生可可碱和咖啡因。这些Mascarocoffea物种的叶片中腺嘌呤的挽救活性较低，但其降解活性却比Coffea canephora中的更高。研究了咖啡因叶中嘌呤核苷，[8-14C]肌苷，[8-14C]鸟苷和[8-14C]黄嘌呤的代谢命运。检测到由这些前体生物合成7-甲基黄嘌呤，但未生物合成可可碱或咖啡因。大量这些嘌呤核苷通过尿囊素分解代谢。挽救了有限量的[8-14C]肌苷和[8-14C]鸟苷，并用于RNA合成，但是未观察到[8-14C]黄嘌呤的拯救。当将[8-14C]可可碱和[8-14C]咖啡因施用于咖啡粉的叶盘上时，几乎未观察到14C代谢物。从这项研究中获得的结果，讨论了Mascarocoffea物种中嘌呤可能的代谢途径。

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