AMP-activated protein kinase (AMPK) plays a role in energy metabolism and glucose homeostasis by monitoring the ratio of ATP to AMP. This kinase can inactivate HMG-CoA reductase and acetyl-CoA carboxylase as well as block the activation of hormone-sensitive lipase by cyclic-AMP-dependent protein kinase (protein kinase A or PKA). SAMS peptide is a synthetic peptide substrate for AMPK based on the sequence around Ser79 (which is phosphorylated exclusively by AMPK) on acetyl-CoA carboxylase. In this sequence, Ser77 (which is phosphorylated exclusively by PKA) is replaced by alanine to eliminate a neighboring binding site for PKA. This substitution yields a substrate more specific for AMPK than acetyl-CoA carboxylase itself. SAMS peptide is phosphorylated rapidly by AMPK, providing a convenient and sensitive tool for assaying AMPK activity.
