Abstract:  The fresh-cut Artemisia selengensis after being removed inedible part,cleaned in ice water and cut,smarshed and centrifuged at 4℃.The obtained crude PPO in the supernatant was used to measure the optimal pH,T and response to phenols.The result showed that the PPO from freshcut Artemisia selengensis shows its greatest activity at 40℃ and pH 6.5,and loss its activity easily when temperature was up 80℃,while the enzyme after being treated at 95℃ for 1min will be inactivated completely.The combining capabilitry of PPO from freshcut Artemisia selengensis to different phenol substrate was in the order:chlorogenic acid and guaiacol > pyrogallic acid > tyrosine > catechol> resorcinol> phenol.The PPO shows the highest activity when combined with catechol.The results also showed that all detected chemical inhibitors can slow down the PPO activity.Among all the inhibitors,pyrosulfite has the strongest effect.It can completely inhibit the PPO activity when its concentration is 0.33mmol/L(i.e.0.06%)in the system,while EDTA-2Na shows the least inhibiting effect,with the other inhibitors in between.28kHz ultrasonic wave treated for 1min can somewhat inhibit the PPO activity.On the contrary the improper ultrasonic treatment can enhance the enzyme activity.

Key words: freshcut, Artemisia selengensis, polyphenol oxidase(PPO), characteristics