Annexin V is a cellular protein which is a part of Annexin group of proteins. It is an anticoagulant protein which by competing for the phosphatidylserine binding sites with prothrombin,inhibits coagulation; additionally, it also inhibits the activity of phospholipase A1. In laboratories, Annexin V is used as a nonquantitative probe to detect  and differentiate apoptotic and necrotic cells from viable cells.