The PI3K comprises of a 110 kDa catalytic subunit and a 85 kDa regulatory subunit. A number of isoforms of the 110 kDa catalytic subunit and the 85 kDa regulatory subunit exist in cells. p85αmodulates the interaction between PI3K and platelet-derived growth factor receptor (1). Furthermore, estrogen receptor isoform ER-alpha binds in a ligand-dependent manner to the p85α regulatory subunit of PI3K. Stimulation with estrogen increases ER-alpha-associated PI3K activity, leading to the activation of protein kinase B/AKT and endothelial nitric oxide synthase (eNOS) (2). MW: 86.0 kDa. Purity ≥95%