The regulatory diversity of the mammalian adenylyl cyclases

Clones for six mammalian adenylyl cyclases have recently been isolated. One of these enzymes, the type I calmodulin-sensitive adenylyl cyclase, is neurospecific and is implicated in neuroplasticity. We propose that the type I adenylyl cyclase may be important for learning and memory because it allows Ca²⁺-amplified cAMP signals, synergism between Ca²⁺ and cAMP-activated kinases, and positive feedback regulation of Ca²⁺ channels by cAMP-dependent protein kinase.