AUTOMATED MEASUREMENT OF ALPHA-AMYLASE ISOENZYMES WITH 6(3)-DEOXYMALTOTRIOSE AS SELECTIVE AMYLASE INHIBITOR

We developed an automated method for measurement of alpha-amylase isoe nzymes in serum by a single kinetic assay (SKA) and a double kinetic a ssay (DKA) with ophenyl-6(5)-azido-6(5)-deoxy-beta-maltopentaoside as a substrate and 6(3)-deoxymaltotriose (DOG3) as a novel selective amyl ase inhibitor. DOG3 showed a large difference in inhibitory activity b etween human pancreatic alpha-amylase (HPA; 86.9% inhibition) and sali vary alpha-amylase (32.1% inhibition) at 0.33 mmol/L. Constant inhibit ion was obtained immediately after addition of DOG3. The inhibitory ef fect did not change with variation in concentrations of amylase up to similar to 3000 U/L. The results obtained by SKA correlated well with those obtained by three methods: monoclonal antibody (r = 0.988), whea t germ inhibitor (r = 0.989), and DKA (r = 0.995). The within-run and between-run CVs for HPA were 0.63-2.32% on SKA, 0.69-1.81% on DKA. No significant interferences by endogenous serum compounds were observed with the proposed methods.