Acts both as an enzyme and as a c-di-GMP sensor to couple transcriptional activity to the c-di-GMP status of the cell (PubMed:26553851). Phosphodiesterase (PDE) that catalyzes the hydrolysis of cyclic-di-GMP (c-di-GMP) to 5'-pGpG (PubMed:15995192, PubMed:24451384, PubMed:26553851). Also acts as a transcription factor to control its own expression (PubMed:26553851). cyclic di-3',5'-guanylate + H2O = 5'-phosphoguanylyl(3'->5')guanosine + H(+) Strongly inhibited by Ca(2+). Optimum pH is 9.35. Is in a fast thermodynamic monomer-homodimer equilibrium. Dimerization is required for PDE activity. Dimerization affinity is increased about 100-fold upon substrate binding. Autoregulated. Directly regulates its own expression in a c-di-GMP-dependent manner. An overexpressed EAL domain (residues 77-362) has similar KM, Vmax, pH and metal dependence and subunit composition as the full-length protein.