Adenylate Cyclase (腺苷酸环化酶)

Adenylyl cyclases (ACs) are enzymes that catalyze the production of cyclic adenosine monophosphate (cAMP) from adenosine triphosphate (ATP). Adenylyl cyclases integrate positive and negative signals that act through G protein-coupled cell-surface receptors with other extracellular stimuli to finely regulate levels of cAMP within the cell. Humans express nine isoforms of membranous ACs and a soluble AC.

Based on regulatory properties, transmembrane ACs are classified into four groups: Group I: Ca²⁺/calmodulin-stimulated AC1, AC3, AC8; Group II: Gβγ-stimulated and Ca²⁺-insensitive AC2, AC4, AC7; Group III: Gαi/Ca²⁺/PKA-inhibited AC5, AC6; Group IV: forskolin/Ca²⁺/Gβγ-insensitive AC9. The soluble AC, unlike the transmembrane ACs, is insensitive to hormones, G proteins and forskolin, a diterpene extracted from the root of the plant Coleus forskohlii that directly activates all isoforms of transmembrane ACs except AC9.