Glycogen synthase kinase (GSK) is a serine/threonine protein kinase that has been implicated in the regulation of cell fate and in the Wnt signaling pathway. Glycogen synthase kinase is an enzyme including GSK1, GSK2, and GSK3. GSK-3 plays an important role in the PI3 kinase and Akt mediated cell survival pathways, and its activity can be inhibited by Akt-mediated phosphorylation at Ser21 of GSK-3α and Ser9 of GSK-3β. GSK-3 has also been implicated in alzheimer’s disease. Six Tau protein isoforms have been identified, all of which are phosphorylated by GSK-3. BioVision’s GSK ELISA kit is a sandwich ELISA assay for the quantitative measurement of GSK in mouse serum, plasma and cell culture supernatants. The density of color is proportional to the amount of GSK captured from the samples.