Adenyl cyclase.

Many hormones interact with their target cells by binding to receptors located on the external surface of the target cells' plasma membrane and subsequently stimulating the enzyme, adenyl cyclase, which is located within the plasma membrane. Stimulation of adenyl cyclase results in formation of cyclic AMP which is released from the membrane into the cell and acts within the cell to regulate a wide variety of cellular processes. In this review, the characteristics of hormone receptors and the relationship between receptor occupancy and adenyl cyclase stimulation are discussed. Our current understanding of the roles of hormones, substrate, magnesium, calcium, and guanine nucleotides as regulators of adenyl cyclase activity is summarized. Because of the central importance of adenyl cyclase and cyclic AMP as mediators of the cellular response to hormones, it is to be expected that many diseases may result from defects in this enzyme system. Indeed, several adenyl cyclase related diseases have been identified and the molecular bases for these diseases are discussed in this review.