Plays an essential role in generating the deoxyribonucleotide precursors dATP AND dCTP for DNA metabolism. The phosphate acceptor specificity is strict toward deoxyadenosine (dAdo) and deoxycytidine (dCyd). The specificity toward the sugar moiety of the nucleoside is less strict. Both 2-deoxyribose, ribose, and arabinose nucleosides are phosphorylated, although the 2-deoxyribonucleosides are preferred. The phosphate donor specificity is dependent on the deoxyribonucleoside substrate, but GTP is efficient with both deoxycytidine and deoxyadenosine. Only nucleoside triphosphates can act as phosphate donors. 2'-deoxyadenosine + ATP = ADP + dAMP + H(+) 2'-deoxycytidine + a ribonucleoside 5'-triphosphate = a ribonucleoside 5'-diphosphate + dCMP + H(+) Deoxyadenosine inhibits deoxycytidine phosphorylation and deoxycytidine inhibits deoxyadenosine phosphorylation. Deoxyadenosine/deoxycytidine kinase is inhibited by both dATP and dCTP. Optimum pH is around pH 8.6. At pH 8.0-9.6 more than 90% of maximal activity is still observed. Homodimer. Belongs to the DCK/DGK family.