Background：

AMP/ATP-binding subunit of AMP-activated protein kinase (AMPK)， an energy sensor protein kinase that plays a key role in regulating cellular energy metabolism. In response to reduction of intracellular ATP levels， AMPK activates energy-producing pathways and inhibits energy-consuming processes: inhibits protein， carbohydrate and lipid biosynthesis， as well as cell growth and proliferation. AMPK acts via direct phosphorylation of metabolic enzymes， and by longer-term effects via phosphorylation of transcription regulators. Also acts as a regulator of cellular polarity by remodeling the actin cytoskeleton; probably by indirectly activating myosin. Gamma non-catalytic subunit mediates binding to AMP， ADP and ATP， leading to activate or inhibit AMPK: AMP-binding results in allosteric activation of alpha catalytic subunit (PRKAA1 or PRKAA2) both by inducing phosphorylation and preventing dephosphorylation of catalytic subunits. ADP also stimulates phosphorylation， without stimulating already phosph