Metabolism of caffeine to nucleic acid precursors in mammalian cells.

Caffeine is rapidly metabolized in human and mouse cells in culture by de-methylation: within 1-3 h of exposure to millimolar concentrations of labeled caffeine, more than 90% of the pool consists of labeled products of metabolism and less than 10% is still caffeine. The methyl groups seem to be transferred and used in the de novo synthesis of thymine, guanine, and adenine to nucleic acids. Normal fibroblasts, Lesch-Nyhan fibroblasts, xeroderma pigmentosum fibroblasts, HeLa cells, wild type mouse cells, and adenine phosphoribosyl-transferase-deficient mouse cells all seem to metabolize caffeine similarly.