乳酸脱氢酶催化反应的热力学研究

Thermodynaic studies of catalytic reaction for LDH

目的 探讨乳酸脱氢酶 (LDH)催化反应的热力学。方法 用Sigma公司生产的LDH ,在生化标准态 (pH7.0 ,2 5℃ ,10 1.3kPa)测定出其催化反应的平衡常数 (Keq) ,吉布斯自由能 (△G0′) ,将以上数值与用热力学公式(△G0′=-nF△E0′,△G0′=-RT1nKeq)计算出的Keq及△G0′相比较。结果 用酶反应测出的Keq =1.1× 10 1 0 mol L ,△G0′=- 5 7.1KJ mol;用热力学公式计算出的Keq =2 .5× 10 4 mol L ,△G0′ =- 2 5 .0 9KJ mol,差异非常显著。结论为了获得Keq及△G0′ 数值 ,应该用Keq =V1 KiQKmp V2 KiAKmB ,△G0′ =-V1 KiQKmp V2 KiAKmB 或Keq =[P][Q] [A][B],△G0′=-RT1nKeq来求取Keq。

Objective To study the thermodynamics of catalytic reaction for LDH.Methods The reaction brought about by LDH(Sigma Chemical Co.)was performed at the biochemical standard state(pH7.0,25℃,101.3kPa).Keq and △G 0′ were obtained,respectively.They were compared with those obtained by calculation of using following thermodynamic equentions:△G 0′ =-nF△E 0′ ,△G 0′ =-Rt1nKeq.Results Keq=1.1×10 10 mol/L,△G 0′ =-57.1KJ/mol were measured by the enzyme reaction;Keq=2.5×10 4mol/L,△G 0′ =-25.09KJ/mol were obtained by calculation.The values with both methods were very different.Conclusion In order to obtain values of keq and △G 0′ ,Keq=V 1K iQ K mp /V 2K iA K mB ,△G 0′ =-V 1K iQ Kmp/V 2K iA KmB or Keq=/,△G 0′ =-RT1nKeq should be used.