漆树漆酶的催化氧化作用　Ⅶ．稀土金属离子对漆酶催化活性的抑制作用

漆树漆酶的催化氧化作用　Ⅶ．稀土金属离子对漆酶催化活性的抑制作用 CATALYZED OXIDATION BY RHUS VERNICIFERA LACCASE Ⅶ.The Inhibition of Enzymatic Activity of Laccase by Rare Earth Metal Ions 王光辉 1 first-author 黄厚评 1 蔡汝秀 1 武汉大学化学系 武汉大学化学系 Department of Chemistry, Wuhan University Department of Chemistry, Wuhan University 以５，６－溴－２，３－二氰基氢醌为底物，在ｐＨ４．０～６．０条件下，用分光光度法考察了稀土金属离子对漆酶催化活性的抑制作用，探讨了抑制特征、抑制位点和作用方式．结果证明，稀土金属离子对漆酶催化活性的抑制属竞争性抑制过程．稀土金属离子的抑制作用是通过它与漆酶活性中心周围的酸性氨基酸残基中的ω－羧基阴离子的配位相互作用实现的；在这种作用下，ω－羧基阴离子对废物酚羟基的氢键或碱催化作用被削弱，使田羟基中的氢以Ｈ＋方式离去的速度受到阻碍．在ｐＨ４．５条件下，Ｌａ３＋离子与ω－羧基阴离子配合反应的解离常数（Ｋｉ）经测定为２．４×１０－６ｍｏｌ·Ｌ－１．研究表明，漆酶分子中的酸性氨基酸残基对于酶－底物复合物的形成及进一步反应，尤其是酚羟基中氢的离去起着十分重要的作用． The inhibition of laccase-enzymatic activity by rare earth metal ions was studied spectrophotometrylys with 5, 6-dibromo-2, 3- dicyanohydroquin one under condition of PH 4. 0～ 6. 0. The results demonstrated that this inhibitory action of rare earth metal ions is a competitive inhibition and the inhibited POSition is the free w-carboxylic group Of acidic amino-acid residues around the copper active site of laccase. The coordination of rare earth metal ions with the free w-carboxylic group anion of acidic amino-acid residues weaken the hydrogen bond or/and basic catalytic action of the w-carboxylic group anion of acidic amino-acid residues with phenolic hydroxy of substrates, consequently, the leaving process of hydrogen on phenolic hydroxy （in the form of H+ ） is hindered and the velocity of the enzymatic reaction slow down obviously. The dissociation constant（Ki） of complexing reaction fo La3+ion with the w-carboxylic group anion of acidic amino acid residues is 2. 4× 10-6 mol. L-1 in pH4. 5condition. The studies showed that the acidic amino acid residues around the copper active Site of laccase play an important role in the formation of enzyme-substrate complex and itS reaction. 漆树漆酶 稀土金属离子 竞争性抑制作用 分光光度法 rhus vernicifera laccase rare earth metal ions competitive inhibition spectrophotometry Q431..361 国家自然科学基金(61672102) 1994-03-01 2021-04-01 3