Phosphodiesterase (PDE) that catalyzes the hydrolysis of cyclic diguanylate (c-di-GMP). Is involved in the modulation of intracellular c-di-GMP levels. Cyclic-di-GMP is a second messenger which positively regulates biofilm formation and negatively regulates virulence in V.cholerae, and is proposed to play an important role in the transition from persistence in the environment to survival in the host. CdpA functions as a repressor of biofilm formation but has no effect on colonization of the infant mouse small intestine. Does not possess diguanylate cyclase (DGC) activity, due to its inactive degenerate GGDEF domain. cyclic di-3',5'-guanylate + H2O = 5'-phosphoguanylyl(3'->5')guanosine + H(+) Is up-regulated during biofilm formation, and is also induced during a late stage of infection of the host. However, cdpA expression is not regulated by c-di-GMP concentration. The EAL domain is required for c-di-GMP PDE activity, and the degenerate GGDEF domain is required for full PDE activity of the EAL domain (PubMed:18227161). The GG(D/E)EF motif in CdpA is degenerate, having the sequence GVGEW. Cells lacking this gene have a level of c-di-GMP almost four-fold higher than that of the respective parent strain. Disruption of this gene also results in increased biofilm formation.