Lipase isoforms and amylase isoenzymes: assays and application in the diagnosis of acute pancreatitis

Pancreatic juice and serum from patients with acute pancreatitis contain three enzymes that have lipolytic activity: L1 and L2, which are pancreatic isoenzymes or isoforms of lipase (EC 3.1.1.3), and L3, which is probably pancreatic carboxyl ester lipase, also known as cholesterol esterase (EC 3.1.1.13). These enzymes are readily separated electrophoretically on agarose and can be developed with an overlay of Kodak Ektachem lipase slide material. The latter acts as a dry-reagent developing substrate, with the enzymes producing blue bands in the slide material. We found L1 in about one-half of normal persons, L2 in none, and L3 in all. We assayed for amylase (EC 3.2.1.1), amylase isoenzymes, lipase, and lipase isoforms in the sera of 100 patients with suspected acute pancreatitis. L2 lipase has the greatest diagnostic efficiency for the diagnosis of pancreatitis, compared with total amylase, P3 amylase, and total lipase. Lipase and L2 could replace amylase, an inefficient test, for the diagnosis of patients with suspected acute pancreatitis. In patients receiving organ transplants, a serum amylase value of greater than 300 U/L or a lipase of greater than 1000 U/L discriminated well between patients with and without complications and (or) acute rejection.