In the small intestine, cholera toxin acts by:
|A||ADP-ribosylation of the G regulatory protein|
|B||Inhibition of adenyl cyclase|
|C||Activation of GTPase|
|D||Active absorption of NaCL|
cAMP — second messenger
1. Its concentration in cells. In cells is regulated by enzyme Adenylyl cyclase
2. Activity of Adenylyl cyclase is regulated by G-regulatory protein.
- G regulatory protein → Gs and Gi
- Gs and Gi are each trimers composed of α (αi or αs), βand γ∼
- GDP-α-βγ-------------→α-GTP + βγ
(inactive G-protein) ß---------------- (active G protein)
a. Heat labile enterotoxin (LT) of E. coli →have similar mechanism of action as cholera toxin.
b. Heat-stable Enterotoxin (ST) of E. coli S causes diarrhea by activating guanylate cyclase →↑cGMP.