**39. Phenylalanine ammonia-lyase and tyrosineammonia-lyase**

Key enzymes of the phenylpropanoid pathway including phenylalanine ammonia-lyase and tyrosine ammonia-lyase are induced in response to biotic (such as chitin from fungal cell walls) and abiotic cues. The elevation of enzyme activity enzymes following application of chitin and chitosan to soybean leaf tissues was dependent on the chain length of the oligom‐ ers and time post-treatment. Treatment with chitin hexamer and chitosan pentamer pro‐ duced the maximal activities at 36 h. Total phenolic content of soybean leaves rose, indicating a positive correlation between enzyme activity and total phenolic content [42].
