Kongming encodes three proteins: KomA, an adenosine deaminase; KomB, a modified HAM1-family purine pyrophosphatase; and KomC, a SIR2-like enzyme with NAD+-degrading activity. The system is activated by phage deoxynucleotide monophosphate kinases (DNKs), which are introduced by infecting phages. In the presence of Kongming, this phage enzyme contributes to the production of deoxyinosine triphosphate (dITP), a base-modified nucleotide that acts as an immune signal. dITP binds to the KomBC complex, triggering the rapid depletion of NAD+, halting cellular activity and preventing phage replication. Structural analyses indicate that KomB has lost its original enzymatic function and now serves as a specialized dITP sensor.