How do GPCRs regulate intracellular cyclic AMP levels?
A．Many？extracellular？signals？acting？via？GPCRs？affect？the？activity？of？the？enzyme？adenylyl？cyclase？and？thus？alter？the？intracellular？concentration？of？the？second？messenger？molecule？cyclic？AMP.
B．Most？commonly,？the？activated？G？protein？α？subunit？switches？on？the？adenylyl？cyclase,？causing？a？dramatic？and？sudden？increase？in？the？synthesis？of？cyclic？AMP？from？ATP.
C．To？help？terminate？the？signal,？a？second？enzyme,？called？cyclic？AMP？phosphodiesterase,？rapidly？converts？cyclic？AMP？to？ordinary？AMP.？Cyclic AMP phosphodiesterase is continuously active inside the cell. Because it eliminates cyclic AMP so quickly, the cytosolic concentration of this second messenger can change rapidly in response to extracellular signals, rising or falling tenfold in a matter of seconds.
D．Cyclic AMP is water-soluble,so it can, in some cases, carry the signal throughout the cell, traveling from the site on the membrane where it is synthesized to interact with proteins located in the cytosol, in the nucleus, or on other organelles. One？way？that？caffeine？acts？as？a？stimulant？is？by？inhibiting？this？phosphodiesterase？in？the？nervous？system,？blocking？cyclic？AMP？degradation？and？thereby？keeping？the？concentration？of？this？second？messenger？high.
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时间：2024-03-20 10:46:25
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