Efficient synthesis of nucleosides

Methods and compositions, including cell cultures, for producing nucleosides are provided which comprise contacting a nucleoside precursor and a sugar moiety donor with a cell containing a nucleoside phosphorylase. The nucleoside precursor can be a purine or pyrimidine base and the sugar moiety donor can comprise a ribose, a deoxyribose, including 2-deoxyribose, or other sugar of choice. The methods and composition can be used to make thymidine from thymine and 2-deoxyinosine or 2'-deoxyadenosine. Other nucleosides, including those having anticancer and/or antiviral properties, also can be obtained according to the invention.