Amylase measurement with 2-chloro-4-nitrophenyl maltotrioside as substrate

The use of 2-chloro-4-nitrophenyl maltotrioside (CNP-G3) as substrate to measure amylase (EC 3.2.1.1) activity in serum directly without the use of auxiliary enzymes was evaluated at two centres. The method was precise (within-run C.V. < 2% and between-run C.V. < 3%), there was no lag phase, background absorbance was low and there were minimal effects of pH changes. When compared with a method which uses 4,6-ethylidene (G7)-p-nitrophenyl (G1)-alpha-D-maltoheptaoside (EPS-G7) as substrate, the CNP-G3 method had greater sensitivity and longer reagent stability (21 days compared with 2 days at 4 degrees C). The activity measured with the CNP-G3 method correlated well with methods using either EPS-G7 and maltotetraose as substrates.