The amylase activity was measured following the method of
Robyt and Whelan (1968) using soluble starch as the substrate. One
unit of amylase activity was defined to hydrolyze 10 mg of starch in
30 min at 37 °C. The lipase activity was determined according to the
method of Winkler and Stuckman (1979). One unit of lipase activity
was expressed as 1 μmol of p-nitrophenyl palmitate (pNPP) released
from the substrate in 1 min at 37 °C. The trypsin activity was assayed
using Na-benzoyl-DL-arginine-p-nitroanilide (BAPNA) as the substrate
(Erlanger et al., 1961). One unit of trypsin activity was calculated
using the amount of trypsin required to release 1 μmol of nitroanilide
from substrate in 1 min at 37 °C. The soluble protein concentration
was measured in diluted homogenates following the Bradford method
(Bradford, 1976) using bovine serum albumin (BSA) as the standard.
The trypsin and lipase activities are both presented as specific activity
Ug−1
of protein, and amylase activity is expressed asUmg−1
of protein.