endo

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  • Created by: jo bill
  • Created on: 22-12-14 12:25

Recap

  1. ligand binds to GPCR
  2. if ligand is an agonist it activates the GPCR
  3. GPCR is able to talk to intracellular G-proteins
  4. G-protein becomes activated- this can be detected becasue alpha-subunit had GTP bound. also alpha-subunit dissociates with BY-subunit
  5. alpha-subunit is a GTPase and therefore kicks off a phosphate to produce GDP. therefore, reassocuition of aby

adenylate cyclase

  • adenylate cyclase is a membrane bound protein - but essentially works as an enzymes
  • it coverts adenosine triphosphate (ATP) to clyclic adenosine monophosphate (cAMP)
  • in mammals, there are 10 different types of adenylate cyclass known

regulation of adenylate cyclase

physiological regualtion

  • G-alphas (stimulatory) are able to activate AC
  • G-alphai (inhibitory) inhibits AC activation

experimental regulation:

  1. forskolin (a labdane diterpene produced in the indian coleus plant) activates AC
  2. chlorea toxin causes ADP ribosylation of G-alphas- therefore alpha unit unable to associate with BY = ^ AC activity
  3. pertussis toxin inhibits Gi so it remains in its inactive form (GDP) bound = ^AC activity

cAMP

  • CAMP CAN ACTIVATE : PROTEIN KINASE A (PKA)
  • as well as:cyclic-nucleotide gated ion channels
  • exchange proteins activated by cAMP (EPACS)

cAMP decomposition:

  1. phosphodiesterase inhibitors
  2. bucladensine

Protein Kinase A (PKA)

  • holoenzyme contains 4 subunits:
  • 2 regulatory subunits
  • 2 catalytic subunits

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