Alkaline phosphatase (ALP) removes phosphate groups from the 5' end of DNA and RNA, and from proteins. Most mammals have 4 different isozymes: placental, placental like, intestinal and non tissue specific (found in liver, kidney and bone). Tissues with particularly high concentrations of ALP include the liver, bile ducts, placenta, and bone. Placental ALP is highly polymorphic, there are at least three common alleles. Damaged or diseased tissue releases enzymes into the blood, so serum ALP measurements can be abnormal in many conditions, including bone disease and liver disease.