Involved in the synthesis of the atypical nucleotide dZTP (2-amino-2'-deoxyadenosine-5'-triphosphate) (PubMed:33926954). Catalyzes the synthesis of N6-succino-2-amino-2'-deoxyadenylate, which undergoes defumarylation and phosphorylation respectively by host PurB and guanylate/nucleoside diphosphate kinases to give dZTP (PubMed:33926954). dZTP is integrated into the viral genome instead of adenine by the viral polymerase. This Z-base probably completely replaces adenosine and forms a triple bond to the opposite T-base (PubMed:33926954). The resulting non-standard viral DNA is called Z-genome (PubMed:33926954). The chemically modified DNA is probably harder for the host bacteria to digest with nucleases or restriction enzymes (Probable). ATP + dGMP + L-aspartate = (2S)-2-amino-2'-deoxyadenylo-succinate + ADP + 2 H(+) + phosphate Purine metabolism. Belongs to the Caudovirales PurZ family.