During the preparation of the enzyme extract, the temperature
was kept at 4 ◦C. The assay medium contained
3 ml of enzyme extract and 2 ml of phenylalanine.
The mixture was incubated at 37 ◦C for 1 h and the reaction
was stopped by adding 0.5 ml of 5 N HCl. PAL
activity was determined by measuring absorbance at
290 nm. One unit of PAL activity was defined as the
change in absorbance per millilitre of enzyme extract.