Serum amyloid P-component (SAP) is also known as Pentraxin 2 (PTX2), APCS, which belongs to the pentaxin family. SAP contains one pentaxin domain. PTX2 is a secreted homopentamer protein which is found in serum and urine. SAP is a precursor of amyloid component P which is found in basement membrane and associated with amyloid deposits. SAP can interact with DNA and histones and may scavenge nuclear material released from damaged circulating cells. SAP may also function as a calcium-dependent lectin. SAP has certain sequence homology with C-reactive protein (CRP).