Human IGFBP-3

Human Insulin-like growth factor binding protein-3 (IGFBP-3) is a 264 amino acid protein which is a member of a family of six circulating proteins that bind IGF-I and IGF-II with high affinity and modulate their metabolic and mitogenic effects. Human IGFBP-3 is a 40-44 kDa glycoprotein that is the most abundant IGFBP in serum and milk. It is produced by non-parenchymal hepatic cells and circulates in serum, binding IGF-I or IGF-II in conjunction with an acid labile subunit (ALS) to form a (1:1:1) 150 kDa circulating complex at a serum concentration of about 100 nM. Phosphorylation of IGFBP-3 also affects its biological activity.