Serum amyloid P (SAP) is a glycoprotein belonging to the pentraxin family of proteins, which has a characteristic pentameric organization and calciumdependent ligand binding. Secreted by liver epithelial cells, SAP is found in serum and urine. Although the function of SAP has not been clearly established, it has been shown to interact with DNA and histones and is thought to play a role in scavenging nuclear material released from damaged circulating cells. Also designated PTX2, SAP is a precursor of the protein amyloid P component (AP), which is universally associated with the amyloid deposits in all forms of amyloidoses, including Alzheimer’s disease. SAP is a decamer of ten identical, noncovalently linked subunits, each of which may be posttranslationally modified by glycosylation.