Abstract
In Coffea arabica leaves, the purine ring of theobromine (3,7-dimethylxanthine) and caffeine (1,3,7-trimethylxanthine) is provided by de novo purine biosynthesis: (a) [14C]glycine, [14C]bicarbonate, and [14C]formate were incorporated into inosine 5[prime]- monophosphate (IMP), sum of adenine nucleotides ([sigma]Ade), theobromine, and caffeine; and (b) incorporation of [14C]formate into IMP, [sigma]Ade, theobromine, and caffeine was inhibited by azaserine, a known inhibitor of de novo purine biosynthesis. Capacity of coffee leaves to salvage added purines was demonstrated by incorporation of [14C]hypoxanthine into [sigma]Ade and the incorporation of [14C]adenosine, [14C]adenine, [14C]inosine, and [14C]hypoxanthine into both theobromine and caffeine. Consistent with synthesis of theobromine from two separate purine nucleotide pools, one synthesized de novo and one via salvage, added xanthine 5[prime]-monophosphate (XMP), inosine, or hypoxanthine failed to reduce the incorporation of [14C]formate into theobromine but diluted the specific radioactivity of [14C]adenosine and [14C]adenine incorporated into theobromine. Evidence that theobromine is not the immediate precursor of caffeine is provided: (a) [14C]xanthine was incorporated into caffeine but not into theobromine; (b) exogenous xanthine diluted the specific radioactivity of caffeine synthesized from [14C]adenine and [14C]hypoxanthine but caused accumulation of radiolabel in theobromine; (c) allopurinol, a known inhibitor of the conversion of hypoxanthine to xanthine, reduced incorporation of [14C]adenine and [14C]hypoxanthine into caffeine but caused accumulation of radiolabel in theobromine; and (d) incorporation of [14C]formate into caffeine, but not into theobromine, was reduced by added XMP, inosine, or hypoxanthine.
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Selected References
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- ANDERSON L., GIBBS M. The biosynthesis of caffeine in the coffee plant. J Biol Chem. 1962 Jun;237:1941–1944. [PubMed] [Google Scholar]
- Anderson J. D. Purine nucleotide metabolism of germinating soybean embryonic axes. Plant Physiol. 1979 Jan;63(1):100–104. doi: 10.1104/pp.63.1.100. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lovatt C. J. De Novo Purine Biosynthesis in Intact Cells of Cucurbita pepo. Plant Physiol. 1983 Nov;73(3):766–772. doi: 10.1104/pp.73.3.766. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PROISER E., SERENKOV G. P. O BIOSINTEZE KOFEINA V LIST'IAKH CHAIA. Biokhimiia. 1963 Sep-Oct;28:857–861. [PubMed] [Google Scholar]
- SHUSTER L. AMINOIMIDAZOLECARBOXAMIDE AND FORMATE INCORPORATION INTO WHEAT EMBRYO PURINES. J Biol Chem. 1963 Oct;238:3344–3347. [PubMed] [Google Scholar]
- Shelp B. J., Atkins C. A. Role of Inosine Monophosphate Oxidoreductase in the Formation of Ureides in Nitrogen-Fixing Nodules of Cowpea (Vigna unguiculata L. Walp.). Plant Physiol. 1983 Aug;72(4):1029–1034. doi: 10.1104/pp.72.4.1029. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Suzuki T., Takahashi E. Biosynthesis of caffeine by tea-leaf extracts. Enzymic formation of theobromine from 7-methylxanthine and of caffeine from theobromine. Biochem J. 1975 Jan;146(1):87–96. doi: 10.1042/bj1460087. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Suzuki T., Takahashi E. Metabolism of xanthine and hypoxanthine in the tea plant (Thea sinensis L.). Biochem J. 1975 Jan;146(1):79–85. doi: 10.1042/bj1460079. [DOI] [PMC free article] [PubMed] [Google Scholar]