High-molecular-weight alkaline phosphatase and alkaline phosphatase lipoprotein X complex in cholestasis and hepatic malignancy.

Alkaline phosphatase (ALP) fast liver isoenzyme is now known as high-molecular-weight ALP. This ALP isoenzyme represents fragments of hepatic cell plasma membranes with various membrane-bound enzymes localized on the surface. High-molecular-weight ALP isoenzyme is present in patients' serum samples in conditions associated with intrahepatic and extrahepatic cholestasis and primary or metastatic hepatic malignancy. High-molecular-weight ALP isoenzyme may coexist with ALP of the normal liver and with ALP lipoprotein X. Alkaline phosphatase ultrafast liver isoenzyme is now known as ALP lipoprotein X complex.