Cl-、NO3-和SO42-离子对漆酶催化活性的抑制作用

The Inhibition of Cl-、NO3- and SO42- Ions on Laccase-enzymatic Activity

关键词:  漆树漆酶  阴离子  竞争性抑制作用  分光光度法

Key words:  Rhus vernicifera laccase  anions  competitive inhibition  spectrophotometry

摘要:

以5,6-二溴-2,3-二氰基氢醌为底物,在pH值4.50条件下,用分光光度法考察了Cl^-、NO₃^-和SO₄^2-离子对漆酶催化活性的影响。发现Cl^-、NO₃^-和SO₄^2-离子对漆酶的催化活性均有不同程度的抑制作用,其最大抑制率分别可达75%、31.4%和17.1%。动力学研究表明,Cl^-、NO₃^-和SO₄^2-离子的抑制作用是瞬时完成的,属于竞争性抑制过程,是通过与底物分子竞争漆酶分子中的Ⅱ型铜(Ⅱ)部位实现的。经测定,Cl^-和NO₃^-离子与漆酶所形成的复合物其解离常数分别为1.12×10^-4 mol·dm^-3和1.78×10^-3 mol·dm^-3。

Abstract:

The influence of Cl^-、NO₃^- and SO₄^2- ions on laccase-enzymatic activity was studied spectrophotometrically by 5,6-dibromo-2,3-dicyanohydroquinone (DDBQH₂) under condition of pH4.50 and 30±0.1℃.The results showed that Cl^-、NO₃^- and SO₄^2- ions had obvious inhibition,and the inhibition ratio of theirs reached to 75%,31.4% and 17.1%,respectively;The kinetic studies demonstrated that the inhibitory actions of Cl^-、NO₃^- and SO₄^2- ions were time independent competitive type,and the inhibited position was the type 2 Cu(Ⅱ) site of laccase.The dissociation constants (K_i) of complexing reaction of Cl^- and NO₃^- ions with type 2 Cu(Ⅱ) site of laccase are 112 and 1780 μmol·dm^-3,respectively.