Figure 1.

cAMP signalling mediated by the HCO₃⁻/CO₂/pH-regulated soluble adenylyl cyclase (sAC). Inside of a cell, carbonic anhydrases (CAs) rapidly interconvert CO₂ and water into HCO₃⁻ and protons. HCO₃⁻ activates sAC, and, due to the nearly instantaneous equilibrium between HCO₃⁻, CO₂ and pH, sAC activity can fluctuate in concert with changes to any of these factors. cAMP produced by sAC will bind to and activate a downstream effector protein (protein kinase A, PKA; exchange proteins activated by cAMP, EPAC; and/or cyclic nucleotide-regulated channels) and be degraded by phosphodiesterases (PDEs) into AMP. LRE1 and KH7 are sAC-specific inhibitors and CAI represents carbonic anhydrase inhibitors.