The temperature dependence of steady‐state kinetics: What can be learned about pig liver esterase stereospecificity?
作者:
Hans Van Gelderen,
Joachim M. Mayer,
Saverio Cellamare,
Bernard Testa,
期刊:
Chirality
(WILEY Available online 1994)
卷期:
Volume 6,
issue 1
页码: 11-16
ISSN:0899-0042
年代: 1994
DOI:10.1002/chir.530060105
出版商: Alan R. Liss, Inc.
关键词: substrate enantioselectivity;product enantioselectivity;chirality;activation enthalpy;activation entropy;chiral HPLC
数据来源: WILEY
摘要:
AbstractThe steady‐state kinetic parameters for pig liver carboxylesterase (PLE)‐catalyzed hydrolysis of the prochiral substrate dimethyl phenylmalonate (DMPM) (product enantioselectivity) and the separate enantiomers of three chiral 2‐phenylpropionic acid esters (substrate enantioselectivity) were measured at seven temperatures between 288 K and 312 K. Arrhenius plots of turnover numbers against the reciprocal of experimental temperatures yielded enthalpies and entropies of activation at enzyme saturation. (+)‐(S)‐methyl‐2‐phenylpropionate, (+)‐(S)‐4‐nitrophenyl 2‐phenylpropionate, and both enantiomers of phenyl 2‐phenylpropionate showed very similar activation enthalpies and entropies (approximately 50 kJ mol−1and −50 J mol−1K−1, respectively), but differences were observed for (−)‐(R)‐methyl 2‐phenylpropionate and (−)‐(R)‐4‐nitrophenyl 2‐phenylpropionate. Whereas the entropies of activation of all 2‐phenylpropionates were negative, positive entropies of activation were measured in the formation of monomethyl phenylmalonate enantiomers from DMPM. Enthalpy–entropy compensation analysis of the data indicates a common mechanism of PLE substrate and product enantiospecificity
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