The substrate 2-chloro-p-nitrophenyl-D-maltotrioside [CNPG3] is hydrolyzed by α-amylase to release 2-chloro-p-nitrophenol [CNP] which is monitored spectrophotometrically at 405 nm. The hydrolysis products also include 2-chloro-4-nitrophenyl-D-maltoside [CNPG2], maltotriose [G3] and glucose [G]. The rate of formation of the 2-chloro-p-nitrophenol is directly proportional to the concentration of α-amylase activity in the sample.
α-amylase
10 CNPG3 -> 9 CNP + 1 CNPG2 + 9 G3 + 1G
Most applications of the procedure have been found to be linear to at least 1,500 U/L amylase.
A reference range for α-amylase in serum in adults measured at 37° C by a similar kinetic method is reported to be 25-125 U/L.
Mean | SD | CV |
58 U/L | 1.2 | 2.1% |
292 U/L | 2.8 | 1.0% |
Mean | SD | CV |
44 U/L | 1.0 | 2.2% |
295 U/L | 5.1 | 1.7% |