text: Wild-type enzymes and variants of CDA (Lys27Gln and Ala70Thr) and DCK (Ile24Val, Ala119Gly, and << Pro122Ser >>) were expressed in and purified from Escherichia coli, and enzyme kinetic parameters were estimated for [[ cytarabine ]] (Ara-C), dFdC, and its metabolite 2',2'-difluorodeoxyuridine (dFdU) as substrates.