BIOL 2021 Lecture Notes - Lecture 12: Adenylyl Cyclase, Protein Kinase A, Cyclic Adenosine Monophosphate
13 May 2018
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• Cyclic AMP (833-836).
• Fig 15-25 cAMP
o Cyclic AMP (cAMP) found in all animal cells and prokaryotes.
• cAMP synthesis
o Made by Adenylyl cyclase from ATP.
o Destroyed by cyclic AMP phosphodiesterase, breaks the bond.
o Stimulatory G protein (Gs) activates adenylyl cyclases (signals activate
GPCRs that are coupled to Gs).
o > increase cAMP production.
o Inhibitory G protein (Gi) inhibits adenylyl cyclase
o > decreases cAMP levels.
o Medically important bacterial toxins, like cholera toxin, act on this pathway.
• Table 15-1 cAMP responses (no need to memorize this table)
o Many different tissues.
o Many different hormones.
o Many different responses.
• Protein kinase A
• Fig 15-26 PKA
o Cyclic AMP dependent protein kinase (PKA) is an enzyme. cAMP exerts
its effects mainly through activating PKA
o PKA = 2 regulatory + 2 catalytic subunits
o cAMP binds to regulatory subunits.
o Releases and activates catalytic subunits.
o PKA phosphorylates serines or threonines on selected target proteins. But
always within some AA sequence (on proteins). Doesn’t phosphorylate
any serine or threonine. The target proteins differ from one cell type to
another, which explains why the effects of cAMP vary so markedly
depending on the cell type.
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