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.