Phosphorylates deoxyguanosine and deoxyadenosine in the mitochondrial matrix, with the highest efficiency for deoxyguanosine (PubMed:10455141). In non-replicating cells, where cytosolic dNTP synthesis is down-regulated, mtDNA synthesis depends solely on DGUOK and TK2. Phosphorylates certain nucleoside analogs (PubMed:10455141). Widely used as target of antiviral and chemotherapeutic agents. 2'-deoxyguanosine + ATP = ADP + dGMP + H(+) 2'-deoxyadenosine + ATP = ADP + dAMP + H(+) Homodimer. Spleen and thymus. Expressed at much lower levels in the brain and liver. Belongs to the DCK/DGK family.