Protein Phosphatase 1, Regulatory Subunit 3 (PPP1R3)

The glycogen-associated form of protein phosphatase-1 (PP1) derived from skeletal muscle is a heterodimer composed of a 37-kD catalytic subunit and a 124-kD targeting and regulatory subunit, referred to as PP1G by Hansen et al. (1995). PP1G binds to muscle glycogen with high affinity, thereby enhancing dephosphorylation of glycogen-bound substrates for PP1 such as glycogen synthase and glycogen phosphorylase kinase . Phosphorylation at ser46 of the PP1G subunit in response to insulin increases PP1 activity, while phosphorylation at ser65 in response to adrenaline causes dissociation of the catalytic subunit from the G subunit and inhibits glycogen synthesis. Because of these functions, PP1G was postulated to be involved in noninsulin-dependent diabetes mellitus (NIDDM) and obesity.