Essential for recycling GMP and indirectly, cGMP. (Microbial infection) Catalyzes the phosphorylation of dZMP to dZDP, when the bacterium is infected by a phage that produces the substrate for the synthesis of dZTP (2- amino-2'-deoxyadenosine 5'-triphosphate), which is then used by the phage as a DNA polymerase substrate. ATP + GMP = ADP + GDP ATP + dZMP = ADP + dZDP Purine metabolism. Belongs to the guanylate kinase family.