adenylatcyklase

Adenylatcyklase, commonly known in English as adenylyl cyclase (AC), is a class of enzymes that catalyze the conversion of ATP to cyclic AMP (cAMP) and pyrophosphate. cAMP serves as a ubiquitous second messenger that relays signals from cell-surface receptors to intracellular targets, thereby regulating diverse physiological processes.

Two major families exist: membrane-bound adenylyl cyclases (ACs 1–9) and soluble adenylyl cyclase (sAC). Most mammalian ACs are integral membrane proteins with cytosolic catalytic domains, whereas sAC is a soluble cytosolic enzyme regulated by bicarbonate and calcium. Membrane-associated AC isoforms display tissue-specific expression and subcellular localization, including at the plasma membrane and organelles, contributing to compartmentalized signaling.

Regulation of AC activity is primarily controlled by heterotrimeric G proteins. Gs alpha activates many AC isoforms to raise cAMP levels, while Gi alpha inhibits them. Additional regulation comes from Gβγ subunits, Ca2+/calmodulin for certain isoforms, protein kinases, and interacting scaffolding proteins such as AKAPs that organize localized signaling domains. Forskolin, a plant-derived compound, directly stimulates many ACs by binding to the catalytic subunit, bypassing GPCR signaling.

Functionally, the produced cAMP activates downstream effectors, chiefly protein kinase A (PKA) and Epac (exchange proteins activated by cAMP). Through these pathways, AC signaling modulates metabolism, ion channel activity, gene expression, and various cellular processes.

Physiological roles are broad, including cardiovascular regulation, nervous system signaling, olfaction (notably certain AC isoforms), and endocrine responses. Abnormal AC signaling has been implicated in metabolic, cardiovascular, and neuropsychiatric disorders, and isoform-specific modulation remains an area of therapeutic interest.