Abstract: The effects of substrate and terminal products on the activities of phenylalanine ammonia-lyase (PAL) in fresh-cut yam. The results showed that the optimum substrate concentration of PAL was 200 mg/L. Although concentration of phenylalanine (Phe) was higher or lower than 200 mg/L, the enzyme activities were inhibited. The trans-cinnamic acid (CA) inhibited the PAL activity, and activity was inhibited most strongly by 120 mg/L CA. Although CA was higher or lower than 120 mg/L, the inhibition decreased. The ferulic acid(FA) inhibited the PAL activity, and effects of 40 mg/L concentration were strongest. With the concentration increased, the inhibition effects decreased. When concentration of FA was 100 mg/L, the effect of inhibition was weakest, then with the concentration increase the effects of inhibition were increased too.

Key words: substrate, products, yam, phenylalanine ammonia-lyase