鲜切芦蒿PPO特性的研究

Characteristics of PPO from Freshcut Artemisia selengensis

芦蒿去除不可食部分、冰水清洗、切分后用研钵碾成匀浆状于低温(4℃)离心机中离心(10000r/min,30min),获得的粗酶液用于多酚氧化酶(PPO)活力的测定和酶特性的研究。结果表明:鲜切芦蒿PPO适宜的pH值为6.5,温度为40℃。鲜切芦蒿PPO对60℃以下的温度不敏感,而在80℃以上温度下很易失活。鲜切芦蒿PPO对酚底物的亲和力依次为:绿原酸、愈创木酚>焦性没食子酸苯酚>酪氨酸>儿茶酚>间苯二酚>苯酚,且与儿茶酚结合时出现最大活力。抑制鲜切芦蒿PPO活力以焦亚硫酸钠效果最好,当其浓度达到0.33mmol/L(即0.06%)时能使PPO完全失活;亚硫酸氢钠和L-Cys的抑制效果也十分强;而EDTA-2Na浓度达3.0mmol/L对鲜切芦蒿PPO的抑制也仅为29.55%,作用很微弱;植酸、AA、醋酸锌、CA和4-HR的抑制作用介于L-Cys和EDTA-2Na之间。

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 lmin 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 lmin can somewhat inhibit the PPO activity. On the contrary the improper ultrasonic treatment can enhance the enzyme activity.