Electrophoretic identification of an isoenzyme of amylase which increases in serum in liver diseases.

Isoenzymes of amylase were studied in serum from 72 persons by means of polyacrylamide gel electrophoresis and a direct saccharogenic assay for amylase activity. In 37 normal individuals, there were two major peaks of amylase actvity with mobilities similar to pancreatic and salivary amylases. In 11 patiets with acute pancreatitis, the area of activity corresponding with pancreatic amylases increased disproportionately. Electrophoretic patterns of amylase activity in normal and pancreatitis urine were almost identical to the respective serum patterns from the same persons. In contrast, a prominent slower-moving peak of amylase activity occurred in the serum of 8 of 12 patients who had hyperamylasemia associated with various liver diseases. Traces of this third peak were identifiable in one-third of normal serum specimens, but no increases in its activity were observed in any specimen from 11 patients with pancreatitis or from 12 other patients with hyperamylasemia unassociated with liver disease. The slower-moving peak was absent from the urine of patients whose serum contained it. The origin of the slower-moving serum amylase appearing in patients with liver disease is not established by these studies. It is possible either that a hepatic amylase is liberated from damaged liver cells or that the metabolism of an amylase not originating in the liver is altered as a result of liver dysfunction.