Test Details: Alkaline phosphatase (ALP) is an enzyme found in many body tissues such as liver, bile ducts, bone, and intestine. There are several different structural forms of ALP called isoenzymes. The structure of the enzyme depends on where in the body it is produced. When the ALP test result is high, you may need to have the ALP isoenzyme test. This test will help determine what part of the body is causing higher ALP levels.