The Role of Xanthosine in the Biosynthesis of Caffeine in Coffee Plants

Biosynthesis and Catabolism of Caffeine in Low-Caffeine-Containing Species of Coffea

“…There was relatively little catabolism of [8-14 C]theophylline by leaves of C. salvatrix, with >90% of the total radioactivity taken up in leaves being the unmetabolized substrate and only minimal incorporation of label into purine catabolites. DISCUSSION The biosynthesis of caffeine in coffee has been investigated primarily in C. arabica (Looser et al, 1974;Baumann et al, 1978;Roberts and Waller, 1979;Baumann and Gabriel, 1984;Suzuki and Waller, 1984a,b;Negishi et al, 1985a;Fujimori and Ashihara, 1994;Ashihara et al, 1996a,b;Mosli Waldhauser et al, 1997;Crozier et al, 1998;Ashihara and Crozier, 1999), and the route illustrated in Figure 1 also operates in tea (Camellia sinensis) (Suzuki and Takahashi, 1976;Negishi et al, 1985b;Ashihara and Kubota, 1986;Fujimori et al, 1991;Negishi et al, 1992;Ashihara et al, 1995Ashihara et al, , 1997Ito and Ashihara, 1999) Although studied in less detail, the main biosynthetic pathway from purine nucleotides to theobromine and/or caffeine appears to be similar, if not identical, in other species of Coffea (Mazzafera et al, 1994) and Camellia irrawadiensis Bold arrows indicate the main pathway via which caffeine is degraded in C. eugenioides. The conversion of caffeine to theophylline is effectively blocked in C. arabica as well as in C. salvatrix and C. bengalensis in which the catabolism of theophylline is also slow.…”