Do organic solvents affect the catalytic properties of lipase? Intrinsic kinetic parameters of lipases in ester hydrolysis and formation in various organic solvents
Do organic solvents affect the catalytic properties of lipase? Intrinsic kinetic parameters of lipases in ester hydrolysis and formation in various organic solvents
复制标题
有机溶剂会影响脂肪酶的催化性能吗？
DOI：
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发表时间：
1995
影响因子：
3.8
通讯作者：
J. Duine
中科院分区：
文献类型：
--
作者：
J. Bert A. van Tol;R.M.M. Stevens;W. J. Veldhuizen;J. Jongejan;J. Duine
当假设有机溶剂不干扰结合过程或催化机制时，底物-溶剂相互作用对酶动力学的贡献可以通过仅用热力学活性替换方程中的底物浓度来解释。从变换中可以看出，只有亲和性参数（Km，Ksp）受此影响。因此，在理论上，这些校正的固有参数（K mint，k spint）和最大速率（V1）的值对于所有介质应该是相等的。对猪胰脂肪酶和洋葱假单胞菌脂肪酶在各种有机溶剂中催化的水解、酯交换和酯化反应进行了测试。通过实验确定的活性系数进行校正，这些溶剂中的基板，或如果不可行，从数据库中的值。然而，尽管校正后各酶在溶剂中的动力学性能变得更加相似，但差异仍然存在。对酶悬浮液的分析揭示了大量颗粒，这解释了酶在有机溶剂中的低活性。然而，没有发现催化可用酶（存在于悬浮颗粒的表面或固定在珠上）的量的估计值和观察到的最大速率之间的相关性。此外，溶剂对悬浮和固定化酶的内参数有相似的影响。溶剂对酶的催化性能的影响的可能原因，在校正溶剂-底物相互作用和参与酶的量后剩余，相对于校正方法所基于的前提进行了讨论。John Wiley & Sons，Inc.
When it is assumed that organic solvents do not interfere with the binding process nor with the catalytic mechanism, the contribution of substrate‐solvent interactions to enzyme kinetics can be accounted for by just replacing substrate concentrations in the equations by thermodynamic activities. It appears from the transformation that only the affinity parameters (Km, Ksp) are affected by this. Thus, in theory, the values of these corrected, intrinsic parameters (K mint , k spint ) and the maximal rate (V1) should be equal for all media. This was tested for hydrolysis, transesterification, and esterification reactions catalyzed by pig pancreas lipase and Pseudomonas cepacia lipase in various organic solvents. Correction was carried out via experimentally determined activity coefficients for the substrates in these solvents or, if not feasible, from values in data bases. However, although the kinetic performances of each enzyme in the solvents became much more similar after correction, differences still remained. Analysis of the enzyme suspensions revealed massive particles, which explains the low activity of enzymes in organic solvents. However, no correlation was found between estimates of the amount of catalytically available enzyme (present at the surface of suspended particles or immobilized on beads) and the maximal rates observed. Moreover, the solvents had similar effects on the intrinsic parameters of suspended and immobilized enzyme. The possible causes for the effects of the solvents on the catalytic performance of the enzymes, remaining after correction for solvent‐substrate interactions and the amount of participating enzyme, are discussed with respect to the premises on which the correction method is based. © 1995 John Wiley & Sons, Inc.
DOI：
10.1073/pnas.89.11.5167
发表时间：
1992-06-01
影响因子：
11.1
作者：
AFFLECK, R;HAYNES, CA;CLARK, DS
通讯作者：
CLARK, DS