金属离子和脲对白蜡虫碱性磷酸酶的影响

各种金属离子及脲对白蜡虫Ericerus pela (Chavannes)碱性磷酸酶的活性有不同的影响。从白蜡虫雌成虫中分离纯化得到碱性磷酸酶，加入各种不同浓度的金属离子及脲测定酶的活力。一价金属离子Na⁺、K⁺、Li⁺对酶活力没有影响。碱土金属离子Ca²⁺、Mg²⁺、Ba²⁺对酶有激活作用，激活作用的大小顺序依次为Ca²⁺、Ba²⁺、Mg²⁺。第一过渡金属离子中，Mn²⁺、Co²⁺、Ni²⁺对酶有激活作用，而Zn²⁺、Cu²⁺有抑制作用。重金属离子Cd²⁺、Pb²⁺对酶有抑制作用。Ca²⁺激活作用表现为非竞争性激活效应。Cu²⁺抑制作用表现为非竞争性抑制效应。脲对碱性磷酸酶有变性失活作用，按脲浓度可分为低于3 mol/L和高于3 mol/L两种类型。低浓度的脲对白蜡虫碱性磷酸酶的活性抑制的动力学表现为混合型效应。

Effects of metal ions and urea on alkaline phosphatase from Ericerus pela (Chavannes)

The effects of metal ions and urea on the alkaline phosphatase (AKP) activity from Ericerus pela (Chavannes) were surveyed. The enzyme was purified from the female adult. After each metal ion and urea had been mixed with the enzyme, the enzyme activity was determined. K , Na and Li had not any effect on the enzyme activity. Ca 2 , Ba 2 , Mg 2 , Mn 2 , Co 2 , Ni 2 activated the enzyme. Zn 2 , Cu 2 , Cd 2 and Pb 2 inhibited the enzyme. The Ca 2 was a more efficacious activator and the effect was classified as noncompetitive type. The inhibition of Cu 2 on the enzyme was found to be of noncompetitive type. The AKP was inactivated by urea; the inactivation could be divided into two kinds according to the concentration of the urea: lower than 3 mol/L and higher than 3 mol/L. At lower concentration, the effect of urea on the enzyme displayed a mixed type of inhibition.