Adenylate cyclase
Encyclopedia : A : AD : ADE : Adenylate cyclase
Adenylate cyclase (EC [4.6.1.1], also known as adenylyl cyclase or AC) is a lyase, an enzyme that catalyzes the conversion of ATP to 3',5'-cyclic AMP (cAMP) and pyrophosphate. cAMP is an important molecule in eukaryotic signal transduction, a so-called second messenger. Adenylate cyclase can be activated or inhibited by G proteins, which are coupled to membrane receptors and thus can respond to hormonal or other stimuli. There are nine known adenylate cyclases in mammals.
Structure
Adenylyl cyclase is a transmembrane protein. It passes through the plasma membrane twelve times. The important parts for its function are located in the cytoplasmic N- and C-termini, as well as in the C1 domain, a large loop between transmembrane helices six and seven which also extends into the cytoplasm.Regulation
Adenylate cyclase is stimulated by G proteins, and by forskolin, as well as other class-specific substrates. The classes I, III and VIII are also regulated by Ca2+/calmodulin. In neurons, adenylate cyclases are located next to calcium ion channels for faster reaction to Ca2+ influx; they are suspected of playing an important role in learning processes. This is supported by the fact that adenylate cyclases are coincidence detectors, meaning that they are only activated by several different signals occurring together.
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