GSK3β, active

Glycogen synthase kinase-3 (GSK-3) is a protein kinase that was originally identified as a regulator of glycogen synthase, a key enzyme in glycogen metabolism. There are two isoforms of GSK-3, GSK-3a and GSK-3b, and they are strictly regulated via phosphorylation. Phosphorylation of GSK-3b on Ser9 by protein kinase B (PKB) causes its inactivation and is the primary mechanism responsible for growth factor inhibition of this kinase. Activation of GSK-3b is dependent upon the phosphorylation of Tyr216. Upon activation, it has been shown to phosphorylate a number of different cellular proteins, including p53, c-Myc, c-Jun, heat shock factor-1 (HSF-1), and cyclin D1. GSK-3b also has been shown to phosphorylate aberrant sites on the microtubule associated protein tau, which is critical for the progression of Alzheimer’s disease. The inhibitors may have therapeutic opportunities for the treatment of diabetes, Alzheimer's disease, stroke and bipolar disorder. EMBL L33801, possessing the amino acid residue substitution H350L. This conflict is reported in theGenBank EST’s AI761503 and AL521664, and the March updated version of Swiss Prot P49841.