Theacrine (1,3,7,9-tetramethyluric acid) synthesis in leaves of a Chinese tea, kucha (Camellia assamica var. kucha).
Theacrine (1,3,7,9-tetramethyluric acid) and caffeine were the major purine alkaloids in the leaves of an unusual Chinese tea known as kucha (Camellia assamica var. kucha). Endogenous levels of theacrine and caffeine in expanding buds and young leaves were ca. 2.8 and 0.6-2.7% of the dry wt, respectively, but the concentrations were lower in the mature leaves. Radioactivity from S-adenosyl-L-[methyl-14C]methionine was incorporated into theacrine as well as theobromine and caffeine by leaf disks of kucha, indicating that S-adenosyl-L-methionine acts as the methyl donor not only for caffeine biosynthesis but also for theacrine production. [8-14C]Caffeine was converted to theacrine by kucha leaves with highest incorporation occurring in expanding buds. When [8-14C]adenosine, the most effective purine precursor for caffeine biosynthesis in tea (Camellia sinensis), was incubated with young kucha leaves for 24 h, up to 1% of total radioactivity was recovered in theacrine. However, pulse-chase experiments with [8-14C]adenosine demonstrated much more extensive incorporation of label into caffeine than theacrine, possibly because of dilution of [14C]caffeine produced by the large endogenous caffeine pool. These results indicate that in kucha leaves theacrine is synthesized from caffeine in what is probably a three-step pathway with 1,3,7-methyluric acid acting an intermediate. This is a first demonstration that theacrine is synthesized from adenosine via caffeine.
Zheng
Xin-Qiang
XQ
Metabolic Biology Group, Department of Biology, Faculty of Science, Ochanomizu University, Bunkyo-ku, 112-8610, Tokyo, Japan.
Ye
Chuang-Xing
CX
Kato
Misako
M
Crozier
Alan
A
Ashihara
Hiroshi
H
D000241:Adenosine / Q000378:metabolism; D000470:Alkaloids / Q000302:isolation & purification / Q000378:metabolism; D001628:Beverages; D002110:Caffeine / Q000378:metabolism; D028244:Camellia / Q000737:chemistry*; D002250:Carbon Radioisotopes; D008745:Methylation; D015394:Molecular Structure; D018515:Plant Leaves / Q000737:chemistry*; D013194:Staining and Labeling; D013997:Time Factors; D014527:Uric Acid / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000378:metabolism*
D000470:Alkaloids; D002250:Carbon Radioisotopes; D014527:Uric Acid; D002110:Caffeine; C077059:1,3,7,9-tetramethyluric acid; D000241:Adenosine