金属离子对鲍鱼碱性磷酸酶活力的影响

Effect of Metal Ions on the Activity of Alkaline Phosphatase from Haliotis diversicolor

碱性磷酸酶(ALP,EC3.1.3.1)是一种金属酶,其结构的维持和酶活性的表现均需金属离子.本文研究了几种金属离子分别对鲍鱼ALP活力的影响.结果表明,Li+,Na+和K+等正一价碱金属离子对酶活力没有任何效应;碱土金属离子Mg2+,Ca2+和Ba2+对酶有激活作用,其激活程度依次为:Mg2+>Ca2+>Ba2+,而且Mg2+在5.0mmol/L时可以使酶活力提高267%;在过渡金属离子中,Zn2+,Mn2+,Co2+和Cu2+对酶的效应不同,Zn2+、Cu2+为抑制作用,而Co2+、Mn2+表现为激活作用;重金属离子Hg2+、Pb2+、Ag+和Cd2+对酶有抑制作用,其中Hg2+的抑制效应最强,1.0mmol/LHg2+可使酶活力抑制94%.研究Mn2+和Cu2+的抑制类型表明,Mn2+为混合型激活作用,而Cu2+对酶的抑制类型为非竞争性抑制作用,其抑制常数(KI)为0.316mmol/L.

Alkaline phosphatase(EC 3.1.3.1)is a metalloenzyme, which catalyzes the nonspecific hydrolysis of phosphate monoesters.The present paper deals with the study of the effect of some kinds of metal ions on the activity of alkaline phosphatase from Haliotis diversicolor.The positive monovalent alkali metal ions(Li^+,Na^+and K^+)have no any effect on the enzyme and that the acid radicals:SO_4^(2+),Cl^-and NO_3^-do not influence the enzyme activity,either;positive bivalent alkaline-earth metal ions(Mg^(2+),Ca^(2+)and Ba^(2+))activate the enzyme and the order of the activation intensity is following:Mg^(2+)>Ca^(2+)>Ba^(2+).The effect of transition Mn^(2+)and Co^(2+)activate the enzyme,while Cu^(2+)and Zn^(2+)inhibit the enzyme.The activation effects of Mn^(2+)on the enzyme are of mixed type.Heavy metal ions(Hg^(2+),Ag^+,Cd^(2+)and Pb^(2+))inhibit the enzyme too.The inhibition effect of Hg^(2+)is stronger than that of Cu^(2+).The inhibition of Cu^(2+)on the enzyme appears to be a partial noncompetitive type and the inhibition constant(K_I)was determined to be 0.316 mmol/L.