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化学学报
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化学学报 ›› 1998, Vol. 56 ›› Issue (7): 625-630.    下一篇

研究论文

微量热法研究单底物酶促反应的热力学和动力学性质及过渡态的分析

望天志;李卫萍;刘义;万洪文;吴鼎泉;屈松生   

  1. 武汉大学化学系;华中师范大学化学系
  • 发布日期:1998-07-15

Studies on single-substrate enzyme-catalyzed reactions and analysis of transition state by microcalorimetry

WANG TIANZHI;LI WEIPING;LIU YI;WAN HONGWEN;WU DINGQUAN;QU SONGSHENG   

  • Published:1998-07-15

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562

被引次数

1

用LKB-2107型微量热系统, 测定了漆酶催化氧化3, 4-二羟基苯甲醛、邻甲氧基酚、邻苯三酚、3, 4, 5-三羟基苯甲酸反应的热谱图, 利用热谱图计算了米氏常数(Km)、反应速率常数(k2)和热力学参数(ΔrHm, ΔG0, ΔT^≠, Ea, ΔST^≠)。并应用过渡态理论对其催化过程进行了分析。结果表明: 稳定过渡态结构有利于酶促反应, 酶-底物在反应物时相互作用仅仅是降低酶的催化效率。提出两种可能提高酶催化效率的方法。由活化熵(ΔST)<0得出酶-底物在过渡态的结构较酶-底物复合物的结构更为有序。

关键词: 苯甲醛 P, 反应动力学, 苯甲酸 P, 量热法, 过渡态理论, 苯三酚, 热谱, 酚 P, 漆酶, 酶促反应

The reactions between laccase and different substrates (3, 4-dihydroxybenzaldehyde, guaiacol, pyrogallol, gallic acid) have been studied by LKB-2107 batch microcalorimetry system. The Michaelis constant (Km), the rate constant (k2) and thermodynamic parameters (ΔrHm, ΔG0, ΔT^≠, Ea, ΔST^≠) have been determined. The process of the reactions have been analyzed by using the transition state theory. The results show that formation of an enzyme-substrate complex is "anticatalytic". The entire and sole source of catalytic power is the stabilization of transition state; reactant-state interactions are by nature inhibitory and only waste catalytic power. The activation entropy (ΔST^≠ <0) indicated that enzyme-transition structure is bound more tightly than enzyme-substrate complex.

Key words: BENZALDEHYDE P, REACTION KINETICS, BENZENECARBOXYLIC ACID P, CALORIMETRY, TRANSITION STATE THEORY, BENZENETRIOL, THERMOGRAPHY, PHENAL P, LACCASE

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