Determinations of amylase isoenzymes in serum by use of a selective inhibitor.

A simple, rapid screening procedure for determining the relative amounts of pancreatic (P)- and salivary (S)-type amylase in serum is presented, involving incorporation of a selective inhibitor (from wheat-germ) into commercially available BMD Single-Vial Amylase and Beckman Enzymatic Amylase-DS procedures for manual and automated isoamylase measurements. Optimal concentrations of inhibitor inhibit the S-type amylase fraction by 87-88%. In contrast, the pancreatic fraction is inhibited by only 19% in either the manual or automated methods. The degree of inhibition is constant for amylase activities up to at least 520 U/L. Use of the ratio (P-amylase/total amylase activity) X 100 helps differentiate between hyperamylasemia caused by S-type or P-type amylase. In preliminary studies, patients with pancreatitis showed a ratio greater than 70%.