PPP1R3B
Domain
The N-terminal region is required for binding to PP1, the central region is required for binding to glycogen and the C-terminal region is required for binding to PYGL.
Function
Acts as a glycogen-targeting subunit for phosphatase PP1. Facilitates interaction of the PP1 with enzymes of the glycogen metabolism and regulates its activity. Suppresses the rate at which PP1 dephosphorylates (inactivates) glycogen phosphorylase and enhances the rate at which it activates glycogen synthase and therefore limits glycogen breakdown. Its activity is inhibited by PYGL, resulting in inhibition of the glycogen synthase and glycogen phosphorylase phosphatase activities of PP1. Dramatically increases basal and insulin-stimulated glycogen synthesis upon overexpression in hepatocytes (By similarity).
Tissue Specificity
Highly expressed in the liver and, at lower levels, in skeletal muscle, including in vastus lateralis, gastrocnemius and soleus (at protein level). Highest mRNA levels are observed in skeletal muscle, and only moderate levels in liver and heart. Weak expression in placenta and lung.
Alternative names
PPP1R4, PPP1R3B, Protein phosphatase 1 regulatory subunit 3B, Hepatic glycogen-targeting protein phosphatase 1 regulatory subunit GL, Protein phosphatase 1 regulatory subunit 4, Protein phosphatase 1 subunit GL, PP1 subunit R4, PTG