| Modification Notes |
Five-prime-AMP-activated protein kinase, known as AMPK, is a heterotrimeric complex that comprises of a catalytic å subunit, and regulatory ∫ and ©. AMPK protects cells from stresses that cause ATP depletion by switching off ATP-consuming biosynthetic pathways. AMPK is activated by high AMP and low ATP via a mechanism involving allosteric regulation, promotion of phosphorylation by an upstream protein kinase known as AMPK kinase (AMPKK), and inhibition of dephosphorylation. Activated AMPK can phosphorylate and regulate in vivo hydroxymethylglutaryl-CoA reductase and acetyl-CoA carboxylase, which are key regulatory enzymes of sterol synthesis and fatty acid synthesis, respectively. The native ∫1 subunit has been found to be phosphorylated in vivo at three sites, Ser24/25, Ser108 and Ser182. Serine 108 is the major autophosphorylation site on the AMPK∫ subunit and mutation at this site leads to the inhibition of AMPK. |