The nature of the serum alkaline phosphatases in liver diseases.

The two main alkaline phosphatase isoenzymes in serum from patients with extrahepatic biliary obstruction have been purified. Properties of these isoenzymes, such as electrophoretic mobility, separation on gel filtration, ultracentrifugation characteristics, Michaelis constants, and sensitivity to neuraminidase have been studied and compared with the isoenzymes of liver and bile. The results show that there is an abnormal isoenzyme in the serum from these patients and that this isoenzyme is similar but not identical with the main bile isoenzyme. It is suggested that it may be associated with a lipoprotein carrier.