Adenylate cyclase (AC) (AC)

Adenylate cyclase (AC) is a membrane-bound enzyme that catalyzes the conversion of adenosine triphosphate (ATP) into cyclic adenosine monophosphate (cAMP), a vital second messenger (Source: StatPearls, 2023). In the intestinal epithelium, this enzyme plays a central role in regulating fluid and electrolyte transport across the cell membrane by modulating ion channels like the cystic fibrosis transmembrane conductance regulator (CFTR) (Source: PubMed, PMID: 16112111). Its activity is typically modulated by G protein-coupled receptors, where Gs stimulates and Gi inhibits the enzyme (Source: UniProt, 2024). Pathologically, certain bacterial enterotoxins, such as those from Vibrio cholerae or enterotoxigenic Escherichia coli, cause the constitutive activation of adenylate cyclase (Source: NIH, 2022). This leads to an overproduction of cAMP, which triggers massive secretion of chloride and water into the intestinal lumen, manifesting as severe secretory diarrhea (Source: Wikipedia, 2024). Pharmacological intervention often involves the use of somatostatin analogs like octreotide, which bind to Gi-coupled receptors to reduce adenylate cyclase activity and alleviate symptoms (Source: PubChem, 2024).

Other names

Adenylyl cyclaseATP pyrophosphate-lyaseAdenylate cyclase 6ADCY6Adenylate cyclase 9ADCY9Adenylate cyclase type 6Adenylate cyclase type 9

The primary mechanism of action for drugs targeting this enzyme in the intestine involves the modulation of intracellular cAMP levels. Somatostatin analogs like octreotide act as agonists at G protein-coupled somatostatin receptors (primarily SSTR2 and SSTR5), which are coupled to inhibitory G proteins (Gi). Activation of Gi leads to the inhibition of adenylate cyclase, thereby reducing the production of cAMP and decreasing the activity of the CFTR chloride channel, which ultimately suppresses fluid secretion (Source: DrugBank, 2024). Conversely, research tools like forskolin directly activate the enzyme to increase cAMP, while bacterial toxins like cholera toxin cause irreversible activation by ADP-ribosylating the Gs alpha subunit (Source: StatPearls, 2023).